Abstract： Objective To detect the serum levels of isocitrate dehydrogenase 1 ( IDH1) and cytokerantin-19 ( Cyfra21-1 ) in non-small cell lung cancer ( NSCLC ) patients ,and evaluate the clinical value of serum IDH1 combinded Cyfra21-1 in NSCLC patients .Methods The NSCLC group were 247 patients recruited from May 2016 to August 2018 in Beijing Chest Hospital affiliated to Capital Medical University ( Including 67 cases of squamous cell carcinoma ,180 cases of adenocarcinoma ,69 cases of stage Ⅰ + Ⅱ ,178 cases of stage Ⅲ + Ⅳ ) .The benign disease group were consisted of 80 patients ,including pulmonary tuberculosis ,pneumonia and benign nodule of the lung .The healthy group were 50 healthy staffs of Beijing Chest Hospital .The 3 groups levels of IDH1 and Cyfra21-1 were detected by enzyme linked immunosorbent and flow fluorescence method , and analyzed the clinical value of the 2 tumor markers in diagnosing NSCLC .Results The levels of IDH1 and Cyfra21-1 in NSCLC were higher than those of healthy group and benign disease group , the differences had statistical significance ( Z = 6 .414 ,6 .811 ,both P < 0 .001) .In different pathology type of NSCLC patients ,the level of Cyfra21-1 was higher in squamous cell carcinoma than that of adenocarcinoma ,the differences had statistical significance ( Z = 2 .114 , P < 0 .05) .&nbsp;The sensitivity of IDH1 combinded Cyfra21-1 in NSCLC was 61 .9％ ,which was higher than that of single tumor marker .In different TNM stages of NSCLC patients ,the sensitivity of IDH 1 was 44 . 9％ in early NSCLC stages Ⅰ and Ⅱ ,which was higher than that of Cyfra21-1 ( 14 .5％ ) . Conclusions Combined detection of serum IDH1 and Cyfra21-1 has good clinical application value in auxiliary diagnosis and differential diagnosis of NSCLC .