The definition of residual gastric cancer lacks uniform regulations. The criteria of the National Gastric Cancer Surgery Collaborative Group for residual gastric cancer are: cancer occurring in the residual stomach more than 3 years after gastric surgery for benign gastric disorders and more than 5 years after gastrectomy for gastric cancer. The endoscopic group, on the other hand, advocates cancer occurring in the residual stomach more than 5 years after gastrectomy for non-gastric cancer lesions. However, Liu Gengnian et al. believe that cancer occurring in the remnant stomach after the initial partial gastrectomy is always called remnant gastric cancer. There can be three cases: (1) New cancer of the remnant stomach, which occurs in the remnant stomach more than 10 years after partial gastrectomy for benign or malignant diseases. (2) Recurrent cancer of the remnant stomach, which is recurrence of cancer in the remnant stomach after surgery for gastric cancer. (3) Residual gastric pre-existing cancer, i.e. cancer that was missed in the stomach during the initial gastric surgery or in the broken end. Currently, it is thought to be related to the destruction of mucosa and mucosal changes caused by the return of alkaline intestinal fluid (including bile fluid and pancreatic fluid) into the stomach due to the decrease of gastrin secretion.