Objective To study the relationship between homocysteine (Hcy)and carotid atherosclerosis in patients with cer-ebral infarction.Methods During January and November 2013,281 patients with cerebral infarction from Affiliated Hospital of Yan’an University were provided the blood samples as cerebral infarction group,140 healthy volunteers served as control group.Serum Hcy was detected by enzymatic cycle assay.According to the results of carotid artery ultrasonography,cerebral infarction group was divided into five groups:artery normal group,intimal thickening group,soft plaque group,mixed plaque group and hard plaque group.The statistically significance was analyzed by SPSS 19.0.Results The serum Hcy level of cer-ebral infarction group was 19.78 ± 5.21 μmol/L,significantly higher than the control group 10.24 ± 3.33 μmol/L (P <0.001).The serum Hcy levels of control group,artery normal group,intimal thickening group,soft plaque group,mixed plaque group and hard plaque group were 10.24±3.33,15.20±2.99,17.03±1.85,25.44±4.24,19.65±4.74 and 18.31 ±3.67 μmol/L respectively.The differences between groups were statistically significant in addition to intimal thickening group and hard plaque group (P =1.106).The positive rates were 16.4%,53.7%,87.1%,95.7%,83.1% and 77.3% re-spectively,the groups which in cerebral infarction group compared with control group,the differences were statistically sig-nificant (P <0.001).Conclusion Hcy played an important role in the occurrence and development of cerebral infarction. Lower serum Hcy concentration,may be an effective way to prevent carotid atherosclerosis and cerebral infarction.