Purpose To investigate the predictive value of serum biomarkers such as AEC、Neutrophil- lymphocyte ratio (NLR) and platelets - lymphocyte ratio(PLR) on immune-related adverse events (irAEs) during the PD-1/PD-L1 inhibitors treatment in advanced malignant tumors. Methods We retrospectively analyzed 95 advanced cancer patients treated with PD-1/PD-L1 inhibitor from January 1, 2017 to May 1, 2020 in our cancer center. Then, the associations between irAEs and PD-1/PD-L1 inhibitors respond was analyzed and the predictive value of serum biomarkers on irAEs occurrence risk was evaluated. Results The incidence of irAEs was 55.8%. There were no statistically significant differences between the irAEs group and the no-irAEs group in Objective response rate (ORR) and Disease control rate (DCR), but the Landmark analysis showed that the irAEs group had better survival after 120 days compared with the no-irAEs group. The incidence of irAEs in the high-AEC and low-NLR groups was greater than that in the low-AEC and high-NLR groups.Univariate logistic analysis results showed that low-NLR, ECOG (0-1) and High-AEC were risk factors for irAEs. However, multivariate logistic analysis not only shows that AEC is an independent factor of irAEs , but also suggests that good ECOG may be more prone to irAEs . Conclusions IrAEs may show a survival benefit to a certain extent. Baseline AEC is a strong predictor of irAEs in the treatment of PD-1/PD-L1 inhibitors.