Causing stool to become thin and triangular may be related to physiological factors such as diet, or pathological factors such as anal fissure, hemorrhoids, intestinal spasm and colorectal cancer. 1. Physiological factors: If the fiber content in the diet is relatively low, it will cause a decrease in the amount of stool, and the situation of stool becoming thin and triangular may occur, so you need to eat more fiber-rich foods, such as celery and so on. Meanwhile, you also need to pay attention to drinking water and moderate activity in daily life. 2. Pathological factors: If there are factors such as abnormal intestinal dynamics or tumor invasion, which can cause narrowing of the intestines or anus, it may lead to stool thinning into a triangle, such as anal fissure, hemorrhoids, intestinal spasm, colorectal cancer and other diseases. There are many other reasons that cause stool to become thin and triangular, if the symptoms are serious, or continue to fail to improve, it is recommended to go to a regular hospital in time, after clarifying the cause of the disease, targeted treatment under the guidance of the doctor, in order to reduce the adverse effects of the disease.