In the first year of the New Year (AD 23), the first emperor, Liu Xuan, proclaimed himself emperor, and Sanfu area was invaded by mutinous soldiers one after another. People are shocked and frightened. Powerful clans and extended families fight to protect themselves, and no one wants to take the lead. Liu Xuanping often heard Ji Guo's reputation and called him Zuo Fengyi to appease the people. In the first year of Jianwu (AD 25), Emperor Guangwu Liu Xiu ascended the throne and proclaimed himself emperor, established the Eastern Han regime, appointed Ji Guo as Yongzhou Pastor, and was later transferred to Shangshuling. Ji Guo gave advice to Guangwu many times. In the fourth year of Jianwu (AD 28), Ji Guo became the satrap of Zhongshan. In the fifth year of Jianwu (AD 29), Chong Peng was destroyed at the end of the Eastern Han Dynasty, and Ji Guo was transferred to Yuyang Prefecture. Yuyang has suffered from the turmoil of the follwed period, and Chong Peng was defeated. People are cunning and bad, and thieves and robbers are everywhere. When Ji Guo arrived in Yuyang, he announced that the people would be rewarded for their meritorious service and killed the thief's head, and the thief's head was scattered. At that time, the Huns invaded the county boundaries of the Eastern Han Dynasty many times, and the border people suffered greatly. Ji Guo reorganized its military forces and designed strategic measures for attack and defense. Huns dare not leave and invade the eastern Han border again, so that people can live and work in peace and contentment. Five years after Ji Guo took office, the number of registered permanent residence has doubled.
Later, thieves rose in Yingchuan area. In the ninth year of Jianwu (AD 33), the court conferred Ji Guo as the prefect of Yingchuan. When Ji Guo was summoned to say goodbye, Emperor Guangwu comforted him, calling him a virtuous satrap, hoping that his local post would bring good influence to Beijing, and said that although he was proficient in hunting, the mountain road was dangerous, so he must be careful. After arriving in Yingchuan, hundreds of people were recruited, including Mountain Thief and Wu of Xiangcheng. All these people surrendered to Ji Guo, and Ji Guo sent them back to their hometown to farm. He wrote to impeach himself and took the initiative. Guangwudi appreciated his strategy, so he didn't blame him. After that, Zhao Hong and Wu Zhao's henchmen heard that Ji Guo's prestige and loyalty came from Jiangnan, and some people defected from hidden places and Hebei. At that time, many people in the imperial court recommended Ji Guo as a general, but Emperor Guangwu didn't call him, because there were Fang Lu in some areas of Bingzhou at that time, and the Xiongnu had not been settled, so he wanted Ji Guo to work here for more time. Ji Guo knew that Fang Lu had been a thief for a long time, and it was difficult to subdue him at once. Therefore, he often strictly abides by the beacon tower and publicly offers a reward to arrest him, so as to divide the thieves. Sui Yu, the Ministry of Fang Lu, conspired to coerce Fang Lu into surrendering to Ji Guo and fled to Xiongnu with Fang Lu.
Later, Ji Guo resigned from the court on the grounds of old age and illness. In the 22nd year of Jianwu (AD 46), Ji Guo was recruited by the imperial court as a traditional Chinese medicine practitioner, and gave his family a house, a tent and money. Ji Guo immediately distributed these items to his relatives, and he didn't keep them at all. In the 23rd year of Jianwu (AD 47), Ji Guo died at the age of 86. Guangwudi personally went to offer condolences and opened a cemetery for him.