There are several reasons for postoperative diarrhea in gastric cancer patients: 1. There is a period of active recovery of intestinal function after surgery, and the function of gastrointestinal tract is easily disordered, so food passes through the gastrointestinal tract for a shorter period of time and is prone to diarrhea; 2. Some of the surgical methods for gastric cancer change the path of food travel, which leads to diarrhea because it has been discharged without time to be absorbed; 3. whether there are infections and so on causing gastrointestinal tract dysfunction are all related. Therefore, once diarrhea occurs after gastric cancer surgery, do not be anxious. Generally speaking, it does not matter if there is an increase in the number of stools, because basically the nutrition is absorbed. For patients with severe diarrhea, it is recommended to take drugs for diarrhea, including montelukast. However, most patients advocate having a healthy and balanced diet after surgery, and there are certain requirements for dietary protein and fat. So guiding a good diet for gradual recovery may not require medication and diarrhea can be relieved.