Gastric cancer is one of the most commonly occurring cancers and the third leading cause of cancer-related deaths worldwide, especially in China[1,2]. If a patient has a stage I-III gastric cancer, surgical resection offers the only realistic chance for cure[3]. For advanced gastric cancer, chemotherapy and targeted therapy is selected in the past[4,5]. Although the approval of several novel chemotherapy and targeted therapy drugs, the prognosis of most patients with advanced gastric cancer still remain dismal.[6] Immunotherapy,such as programmed death-ligand 1/programmed death-1(PD-L1/PD-1) inhibition, is being increasingly recognized as an effective treatment against various cancers[7,8]. The first immunotherapy drug to be approved for gastric cancer was pembrolizumab based on a 22％ objective response rate (ORR) in PD-L1 positive advanced gastric cancer patients and an 11.6％ ORR in PD-L1 non-selected patients[9].