Gastric cancer is usually staged clinico-pathologically by traditional depth of tumor invasion (T), lymph node metastasis (N) and distant metastasis (M), which can be divided into stages I~IV, and the later the stage, the worse the prognosis. In clinical practice, it is found that this TNM staging is not meticulous enough to judge the prognosis of gastric cancer. That is to say, this staging model is inaccurate in judging the recurrence and prognosis of some gastric cancer patients. Some patients with the same stage III can have a longer survival time, while others have recurrence and metastasis quickly. We found a very helpless phenomenon in the clinic: most patients with gastric cancer, whether operated or not, with or without distant metastasis, will have diffuse abdominal dissemination and ascites, and if not effectively controlled, peritoneal thickening and masses will soon appear, and various intra-abdominal ducts will then be compressed and lead to intestinal obstruction, biliary obstruction, ureteral obstruction, and eventually incurable. In 2012, Seoul National University School of Medicine in Korea published their prognosis analysis of 1072 cases of gastric cancer in British Journal of Surgery. They found that checking the presence of tumor cells in the peritoneal lavage fluid during gastric cancer surgery (if positive predicts that tumor cells have undergone peritoneal dissemination) to determine the good or bad prognosis of gastric cancer is a more realistic reflection of the disease and is more valuable than the traditional T/N/M index. The famous Memorial Sloan-KetteringCancer Center in the United States used the molecular biology technique (PCR) to check the intraoperative lavage fluid CEAmRNA of gastric cancer to reflect the dissemination of tumor cells, and the result of positive PCR has a much worse prognosis than negative patients, and the sensitivity is very high. At present, this technique can be routinely carried out in the Cancer Center of Gulou Hospital, which can provide fine disease analysis for gastric cancer patients, and then lay the scientific foundation for the establishment and application of subsequent fine chemotherapy mode.