Objective To explore the effect of Immune checkpoint inhibitors (ICIs) on coagulation function in the treatment of advanced lung cancer. Methods In this study, 60 patients with advanced lung cancer admitted to Bazhou People's Hospital who were suitable for the application of ICIs were treated with fasting fresh venous blood of 3 mL before and after each treatment cycle. The changes of thrombin time (APTT), prothrombin time (PT), thrombin time (TT), D-dimer (D-D) and fibrinogen (FIB), D-dimer and platelet before and after the first and second cycles of ICIs treatment were examined. Results APTT and PT decreased after the first cycle of immune checkpoint inhibitors, statistically significant (P<0.05). PLT, D-D, TT, and FIB were also decreased compared with those before treatment, but the difference was not statistically significant (P>0.05). There was no significant difference in coagulation function after the second cycle of treatment compared with before treatment (P>0.05). The second cycle was prolonged by PT, TT compared to the first cycle, with statistically significant differences (P<0.05).Conclusion APTT and PT decrease after the first cycle of ICIs treatment, which increase the risk of hypercoagulability or thrombosis in advanced lung cancer patients to a certain extent. However, PT and TT prolonge after the second cycle of treatment, suggesting that the hypercoagulable state or the risk of thrombosis will be reduced after effective treatment