Chemotherapy for gastric cancer means the treatment of gastric cancer patients with chemical drugs. For early stage gastric cancer patients with metastatic lymph nodes and all patients with progressive gastric cancer, chemotherapy is needed. For early stage gastric cancer patients without any metastases, surgery alone can achieve curative effect and chemotherapy is not needed. Chemotherapy is divided into pre-operative chemotherapy, intra-operative chemotherapy and post-operative chemotherapy. The purpose of chemotherapy is to confine the cancer foci, destroy the remaining cancer foci and prevent cancer recurrence and metastasis. The commonly used chemotherapy drugs are fluorouracil, tegafur, mitomycin, adriamycin, etc. Chemotherapy often causes serious adverse reactions, such as nausea, vomiting, dizziness, loss of appetite, poor appetite, etc. Patients can consult their specialist for details.