Objective:To analyze the prognostic value of the coagulation index in stereotactic radio surgery(SRS)for patients with non-small cell lung cancer(NSCLC)and brain metastases(BMS).Methods:We retrospectively analyzed clinical data from 512 patients diagnosed with NSCLC and BMS,who were treated with SRS at Tianjin Huanhu Hospital from October 2015 to September 2018.The overall survival(OS)and progression-free survival(PFS)rates were analyzed.The Cox model was employed to examine prognostic factors.Subsequently,the receiver operating characteristic(ROC)curve was constructed based on multi-factor analysis usin the Cox model.The area under the ROC curve(AUC)was used to assess the prognostic value of coagulation indexes in patients with NSCLC and BMS who underwent SRS.Results:In 1,2,3,and 4 years,PFS rates were 79.9%,69.9%,56.6%,and 43.2%,respectively,and OS rates were 93.4%,83.2%,69.9%,and 57.6%,respectively.Smoking and average fibrinogen(Fib)levels,prothrombin time(PT),and D-dimer(D-D)levels were correlated with a longer PFS(P<0.05).Av-erage activated partial thromboplastin time(APTT),Fib,and D-D levels were correlated with a longer OS(P<0.05).Smoking and mean Fib and D-D levels were significantly correlated with a longer PFS(P<0.05),while The average levels of Fib and D-D are each significantly associated with longer OS rates(P<0.05).The combined detection of Fib and D-D in predicting the prognosis of NSCLC patients with brain metastases undergoing SRS treatment shows a significantly higher AUC compared to the detection of Fib and D-D individually(P<0.05).Conclusions:Co-agulation indexes have a certain correlation with the prognosis of patients with NSCLC and BMS treated with SRS.Furthermore Fib and D-D are independent risk factors for the prognosis of these patients and can be used to assess their outcomes.The combined evaluation of the indexes provides a more ideal prognostic assessment.