The first part of the stool is normal and the second part becomes thin may be physiological phenomenon, may also be the colon occupational lesions. 1. Physiological phenomenon: the human body before defecation excreta will be stored in the large intestine, the longer the storage time, the water in the excreta will be further dehydration phenomenon, the appearance of the front part of the normal after the thinning of the situation. 2. Occupational lesions of the colon: such as colorectal polyps, colorectal cancer, colorectal mucosal fibroma and other diseases, can also cause the occurrence of such adverse symptoms, due to the occurrence of local occupational lesions of the colon will lead to part of the excretory obstruction, causing feces to appear in the front section of the normal after the section becomes thin, often accompanied by pain in the lower abdomen, blood, pus, defecation difficulties and other adverse symptoms, but also may have lethargy, fatigue, anemia and other symptoms of the alarm. The symptoms may also include lethargy, fatigue, anemia, and other alarm symptoms. In daily life, we should pay attention to dietary hygiene, reasonable diet, balanced nutrition, regular diet, low-fat, low-salt diet. Eat less fried and stimulating food. Eat less soybean products and peanut products. Eat less cold dishes, no cold drinks, avoid smoking and alcohol. It is recommended to go to the regular hospital to improve the stool routine, colonoscopy and other tests to avoid delaying the condition.