Objective:To explore the characteristics and influencing factors of immune-related adverse events(irAEs)in ad-vanced gastric cancer patients treated with PD-1/PD-L1 inhibitors,analyse clinical features associated with prognosis.Methods:A ret-rospective analysis was conducted on the clinical data of 60 patients with advanced gastric cancer.Based on the occurrence of irAEs,the patients were divided into an irAEs group(n=32)and a non-irAEs group(n=28).Immune-related adverse reactions were assessed using the Common Terminology Criteria for Adverse Events(CTCAE 5.0).Short-term efficacy was evaluated using the Response Evalu-ation Criteria in Solid Tumors(RECIST 1.1).Long-term efficacy was assessed using overall survival(OS)and progression-free surviv-al(PFS).A multivariate Logistic regression model was employed to analyze the factors influencing the occurrence of irAEs.The Kap-lan-Meier survival curve was used to evaluate the impact of clinical characteristics on prognosis,and the Cox proportional hazards model was used to analyze the clinical characteristics affecting patient prognosis.Results:The Ki-67 index in the irAEs group was higher than that in the non irAEs group,and the pepsinogen Ⅱ level was lower than that in the non irAEs group(P＜0.05).Multivariate Logistic regression analysis showed that the Ki-67 index was a risk factor for the occurrence of irAEs(P＜0.05).There was no statistically sig-nificant difference in treatment efficacy between the two groups of patients(P＞0.05).Prognostic analysis showed that OS and PFS in TNM stage Ⅲ patients were higher than those in stage Ⅳ patients(P＜0.05),the median PFS of HER-2 positive patients was higher than that of negative expression patients(P＜0.05).Cox regression analysis indicated that TNM staging and HER-2 expression were independent risk factors for PFS in patients(P＜0.05).Conclusion:The incidence of irAEs in the treatment of advanced gastric canc-er with PD-1/PD-L1 inhibitors is relatively high,but most irAEs are low-grade,indicating a high level of safety.The Ki-67 index is an independent risk factor for the occurrence of irAEs.Patients with stage Ⅲ TNM have longer OS and PFS compared to those with stageⅣ,and patients with positive HER-2 expression have longer PFS.