Watery stool with fishy odor may be caused by acute enteritis, allergic diarrhea, drug overdose and other factors. 1. Acute enteritis: when the intestinal mucosa is infected by bacteria, viruses and other pathogenic microorganisms and inflammation occurs, may lead to intestinal mucosal congestion and edema, on the one hand, affecting the digestive function, on the other hand, it may make a lot of water from the intestinal wall precipitation, in the combined effect of the two, there may be a drainage-like stools with a fishy smell. 2. Allergic diarrhea: If you eat some allergic foods, under the action of allergens in the food, the body may undergo an allergic reaction, and some intestinal contents may not be absorbed by the body before being discharged from the intestines, and watery stools with a fishy odor may also occur. 3. Drug overdose: some drugs such as olmesartan, timosartan, etc., when taking an overdose of diarrhea may occur, coupled with the high protein content of recent food, in the intestinal tract may decompose and produce smelly substances, resulting in the above symptoms. When there is drainage-like stool with fishy smell, you should seek medical treatment in time, complete the stool routine, allergens determination and other tests under the guidance of a professional doctor, to clarify the cause of the disease under the guidance of a professional physician, and active treatment.