Objective To evaluate the rational of peritoneal warm perfusion chemotherapy after the operation. MethodsOne hundred and two patients with gastric cancer were included in this study. One hundred milliliter of peritoneal fluid were collected respectively after opening the abdomen,before closing the peritoneal cavity,and after hyperthermic peritoneal perfusion chemotherapy for free cancer cells examination. ResultsAfter opening the abdomen, the positive rate of free cancer cells was 36.3%(37/102), and the positive rate before closure of peritoneal cavity was 52.9%(54/102), 31 cases of free cancer cells were found killed after the warm perfusion chemotherapy,the effect rate was 57.4%(31/54).The free cancer cells positive rate related to the tumor infiltration depth, serous membrane invasion area and the type of histopathology. Conclusion In the peritoneal cavity of patients with gastric cancer, free cancer cells are able to survive and have a high degree of activity. Hyperthermic peritoneal perfusion chemotherapy is an effective method to kill free cancer cells.