Only fertilized roundworm eggs can cleave and develop. It takes about 10 days to develop into rod-shaped larvae in moist, well-oxygenated, shaded soil at 21~30°C. The eggs shed their skin once and become infective larvae. If swallowed at this time, the egg shell is digested and the larvae escape in the intestines. Then it passes through the intestinal wall, enters the lymph glands and mesenteric veins, passes through the liver, right heart, lungs, passes through the capillaries to the alveoli, then passes through the trachea, epiglottis of the larynx, mouth, esophagus, stomach, and returns to the small intestine. The whole process takes about 25 ~29 days, the skin sheds three times, and then develops into an adult after more than one month. Ascaris is a species distributed worldwide and is the most common parasite in the human body. The infection rate can reach more than 70%, which is higher in rural areas than in cities and in children than in adults. After being infected, symptoms such as fever, cough, loss of appetite or hunger, paroxysmal pain around the umbilicus, malnutrition, insomnia, teeth grinding, etc. may appear in varying degrees, and sometimes serious complications may occur. For example, roundworms can form roundworm intestinal obstruction by twisting into clumps, burrowing into the biliary tract to form biliary ascariasis, and entering the appendix to cause appendiceal ascariasis and intestinal perforation, which are very harmful to the human body. To prevent ascariasis, we mainly need to treat patients universally and eliminate the source of infection; manage feces well; pay attention to personal hygiene and prevent the entry of eggs.