After graduating from college, Sam lived in Washington with his new girlfriend Carly. He had saved the world twice, so he was a little unable to adapt to normal life, but he still found a job and tried to stabilize himself. Come down. But Carly doesn't understand Sam's distress. She works for Dylan Gould, an art and car collector, played by Patrick Dempsey. Living with Sam and Carly are the little Transformer "Runwheel" and his fellow little robot "Brain". At the same time, the Autobots and Major Lennox are fighting the Decepticons, the enemies of mankind, around the world. After a fierce battle with the Driller, Optimus Prime discovered a columnar object belonging to an Autobot ship that they believed to be missing long ago. The Decepticons still remain on Earth, their leader Megatron is now weak after the last war, but he is still planning something. Optimus Prime was angry that humans had concealed the truth from him, especially the Director of National Intelligence, Charlotte Miura. It turned out that American astronauts had discovered the crashed Transformers Autobot spaceship when they landed on the moon many years ago - " The energy pillar in the Ark, but they kept it hidden from the world and the Autobots.

Optimus Prime asked for a trip to the moon, and they quickly arrived there, but did not realize that there was a Decepticon following them. On the moon, Optimus Prime and his team discovered Sentinal Prime, the former leader of the Autobots and Optimus Prime's mentor. The Autobots brought the natural enemy and the five energy pillars around him back to the earth.

At this time, Sam was tortured by his new boss. Then he was recognized by Jerry.wang as a friend of the Transformers. Jerry.wang tried to tell him the Decepticon conspiracy. Obviously, he also was forced into that plan. After a while, the laser bird killed him. Sam hurried to tell the Autobots, but was stopped outside the secret base. Although Director Miying was very reluctant, he could not withstand the insistence of others, so he had to let Sam stay and watch the situation progress. After bringing the Enemy and the five energy pillars back to Earth, Optimus Prime used the leadership module (The Matrix) to restart the Enemy, and then put it back into his body. It turns out that those energy pillars are part of the "space bridge". There are hundreds of them, and now they don't know where they are scattered. Director Miying began to drive Sam home. Sam relied on his own analysis and deduction to figure out what the Decepticons were using humans to do, but no one listened to his analysis, so he decided to ask retired agent Simon (John Turturro) for help. He investigates. Carly is unhappy and complains that Sam wants to save the world again. The two had a fight and broke up. Carly went to her boss Dylan's party alone. Simon wrote a best-selling book about his past experiences and is now living a comfortable life, but he quickly agreed to Sam's request. The two first went to find the astronauts who landed on the moon. They were convinced that these people must know the inside story, but they were all silenced by the government. The old astronauts showed Sam some photos of the back of the moon taken back then. It turned out that there were many energy pillars there. Sam immediately realized that the Decepticons had always known about the "Space Bridge". They were using Optimus Prime to activate the Enemy, because the Enemy was the key to splicing the Space Bridge, and they had to protect him. In the middle, the Decepticon's Dread Troopers chased the Autobots, and Ironhide and Sideswipe successfully defeated them. But the natural enemy rebelled. He killed Ironhide, melted him with a corrosive acid gun, and ran away with the energy pillar. It turns out that Predator believed that the Autobots could never win, so he formed an alliance with Megatron, thinking that peace could be achieved quickly. He originally drove the spacecraft to the Earth to meet Megatron, but both were ambushed by the cunning Starscream, one crashed into the moon, and the other was planted in the North Pole. Now the Predators and Megatron can start their grand plan again. They awaken the secret Decepticon army ambushing on the moon and send them to the earth through the "space bridge". Seeing so many Decepticons, humans gave up and spread their grievances on the Autobots, asking them to leave the earth immediately. The Autobots had no choice but to prepare to board the spacecraft. At this time, Sam went to the party at Dylan's house to reconcile with Carly. Who would have thought that Dylan was the biggest leader among the humans who helped the Decepticons. He kidnapped Carly and forced Sam to be a spy, providing intelligence on the Autobots to see if they were planning a counterattack. He also sent a Decepticon robot to follow Sam to record the words and deeds of Sam and the people around him. If If Sam disobeys, Carly will die. Sam went to Optimus Prime and the Autobots and asked them what their plans were. Optimus Prime said that they had no plans and would just leave silently. They just left. The spaceship was shot down by Starscream in mid-air, and the Autobots seemed to The entire army has been wiped out. Sam had no choice but to seek help from Epps, a former officer who had transferred to the base, and asked him to help him track Dylan and rescue Carly. After some tracking, they found that Dylan and the others were in Chicago, so Sam, Epps and the latter's military comrades also went to Chicago. Chicago has become a paradise for Decepticons at this time. Fortunately, most of the human survivors have left. Just when Epps and Sam thought there was no hope, the Autobots suddenly appeared! It turned out that everything was planned, and they had secretly escaped from the spacecraft before it exploded. At this time, the Enemies and Megatron are planning to open the space bridge again. This time, they want to transmit the entire Cybertron planet to the Earth and make the surviving humans their slaves.

The Autobots rescued Carly, but also sacrificed two members, Wheeljack and IronHide. They tried to destroy the space bridge from a distance, but failed. Shockwave commanded his pet, the Drill Beast, to collapse Chicago's high-rise buildings and create a mess. At this time, the natural enemy suddenly turned against Megatron, saying that he would no longer work for him, and pushed Megatron off the tall building. The weak Megatron fell and could not get up. Starscream caught Sam and wanted to kill him. Sam shot Starscream in the eye with a hook gun, and then fixed a bomb in Starscream's other eye. Starscream suffered severe injuries and died. Optimus Prime fought with Shockwave, ending his life, and then Optimus Prime used Shockwave's laser weapon to destroy the main control column of the space bridge. Sam also found Dylan at this time and struggled with him. In the end, Dylan's life was ended by the current flowing from the main control column of the space bridge. Optimus Prime began to fight against the Sky Enemy. At this time, the planet Cybertron had begun to teleport over. Optimus Prime was no match for the Sky Enemy at all. Carly ran to Megatron and used the provocation method to prompt Megatron to help Optimus Prime fight against the Sky Enemies. The Enemy was injured and fell down. At this time, Megatron angered Optimus Prime. As a result, Optimus Prime first killed Megatron and then used Megatron's gun to kill the Enemy. In the ruins, Sam and Carly confessed to each other, and Bumblebee made a gear ring and insisted that Sam propose. Optimus Prime's voice sounded, he said that in any war, there will always be a lull in the storm. One day, we will lose confidence; one day, our comrades will betray us...but we will never abandon this planet and its people. I am Optimus Prime, and I send this message to the universe - We are here, we are home.