Abstract： Objective To analyze the diagnostic value of carbohydrate antigen 125(CA125),carbohydrate antigen 199(CA199),cytokeratin 19 fragment(CYFRA-21),and carcinoembryonic antigen(CEA)for brain metastasis in non-small cell lung cancer(NSCLC)patients.Methods A total of 96 NSCLC patients were selected and divided into a metastatic group(32 cases)and a non metastatic group(64 cases)based on the presence of brain metastasis;75 healthy examinees who underwent physical examinations were included in the health group,and fasting venous blood from all study subjects was extracted in the morning,and serum CA125,CA199,CYFRA-21,and CEA levels were detected.Receiver operating curve(ROC)was plotted to analyze the di-agnostic value of combined detection of CA125,CA199,CYFRA-21,and CEA for brain metastasis in NSCLC patients.Results The levels of CA125,CA1 99,CYFRA-21,and CEA in the transfer group were higher than those in the non transfer group and the healthy group,and the levels of CA125,CA199,CYFRA-21,and CEA in the non transfer group were higher than those in the healthy group,with statistical significance(P＜0.05);The ROC results showed that the area under the curve(AUC)for the com-bined detection of CA125,CA199,CYFRA-21,and CEA in diagnosing brain metastases in NSCLC patients was higher than that of CA125,CA199,CYFRA-21,and CEA alone.Conclusion CA125,CA199,CYFRA-21,and CEA are highly expressed in NSCLC patients with brain metastases.The combination of the four can effectively diagnose the presence of brain metastases in patients and has certain diagnostic value.