Objective To explore the effecacy of camrelizumab combined with capecitabine and oxaliplatin (CapeOX) in the treatment of elderly patients with advanced gastric cancer and its effect on T lymphocyte subsets.Methods Eighty elderly patients with advanced gastric cancer enrolled in the hospital between November 2020 and November 2022 were randomly divided into two groups. The control group was treated with CapeOX regimen, and the study group with camrelizumab and CapeOX. The clinical efficacy, toxic and side effects, and the levels of T lymphocyte subsets and tumor markers before and after treatment were analyzed and compared between the two groups.Results After treatment, the clinical effective rate of the study group was significantly higher than that of the control group (P<0.05). As compared with before treatment, the levels of CD4+ and CD3+, and the CD4+/CD8+ were increased, while the CD8+ level was decreased in both groups after treatment (P<0.05). Moreover, the levels of CD4+ and CD3+, and the CD4+/CD8+ in study group were significantly higher and the CD8+ level was lower than those of the control group after treatment (P<0.05). The serum levels of CA199, CEA and CA724 in both groups were decreased after treatment (P<0.05), and those of the study group were lower than those of the control group (P<0.05). No significant differences were found in the incidence of gastrointestinal reactions, bone marrow suppression, liver and kidney damage and peripheral nerve toxicity between the two groups (P>0.05).Conclusion Camrelizumab combined with CapeOX has great efficacy in the treatment of advanced gastric cancer, not only improving immune function, but also inhibiting the levels of tumor markers. In addition, it has no significant increase in toxic and side effects, so it is worthy of clinical application.