Chemotherapy for gastric cancer retroperitoneal metastasis is effective. Using chemotherapy can not only kill free cancer cells in the abdominal cavity, but also remove small metastases, which plays an important role in gastric cancer retroperitoneal metastasis. For chemotherapy for gastric cancer retroperitoneal metastasis, the treatment plan needs to be determined according to the patient’s peritoneal metastasis. For diffuse peritoneal metastases, systemic chemotherapy combined with peritoneal heat infusion chemotherapy can be performed. If the physical condition allows, the combination of systemic chemotherapy and HER2 gene testing will have better therapeutic effect. During chemotherapy for retroperitoneal metastasis of gastric cancer, the drugs can fully act on the lesion site because intraperitoneal chemotherapeutic drugs can directly enter into the abdominal cavity and the large molecule drugs stay in the abdominal cavity for a longer time. Theoretically, the adverse reactions caused by drugs are relatively less. The effect of gastric cancer retroperitoneal metastasis after chemotherapy is not certain. Therefore, surgical patients should be strictly screened, and systematic treatment remains the basis of gastric cancer retroperitoneal metastasis. Postoperative adjuvant therapy should be carried out with reference to the preoperative treatment plan, and physical changes should also be noted.