To analyze correlation among serum homocysteine (Hcy) ,Cysteine C (CysC) levels and severi‐ ty of coronary artery disease .Methods : A total of 220 coronary heart disease (CHD) patients treated in our hospital from Sep 2015 to Dec 2017 were selected as CHD group .According to Gensini score ,CHD group were divided into mild stenosis group (n＝ 63 ) ,moderate stenosis group (n＝ 71 ) and severe stenosis group (n＝ 86 ).Another 200 healthy people were enrolled as healthy control group .Serum Hcy and CysC levels were measured and compared a‐mong all groups .Correlation among serum Hcy , CysC levels and severity of coronary artery disease were analyzed . Results : Compared with healthy control group ,there were significant rise in serum Hcy [ (8.29 ± 1.02) μmol／L vs. (16. 14 ± 3.01) μmol／L] and CysC [ (0. 65 ± 0.11) mg／L vs.(1. 21 ± 0.12) mg／L] levels in CHD group .P＝0. 001 all.Compared with mild stenosis group ,there were significant rise in serum Hcy [(9. 31 ± 1.12) μmol／L vs.(12. 13 ± 3.32) μmol／L vs.(14.61 ± 3.82) μmol／L] and CysC [ (1.05 ± 0.21) mg／L vs.(1. 51 ± 0. 52) mg／L vs.(3.42 ± 1.01) mg／L] levels in moderate stenosis group and severe stenosis group ,and those of severe stenosis group were significantly higher than those of moderate stenosis group , P＝0.001 all.Pearson correlation analysis indicated that serum Hcy ( r＝0.431 , P＝0.004) , CysC ( r＝0.640 , P＝0. 003) levels were significant positively correlated with Gensini score .Conclusion :Serum Hcy and CysC levels is closely correlated with severity of coronary artery disease . Its detect is help for therapeutic effect and prognosis assessment for CHD patients .