Abstract: Objective To explore the clinical diagnostic value of plasma homocysteine (Hcy)in the prognosis of patients with acute cerebral infarction (ACI).Methods According to Hcy median value on admission,78 ACI patients with hyperhomocysteinemia were divided into high-Hcy group and low-Hcy group,and meanwhile 34 ACI patients with normal Hcy level were de-signed as control group.All patients were given the secondary prevention for cerebrovascular dis-ease.On the basis of conventional therapy,high-Hcy group and low-Hcy group were treated with vitamin B12.BI and NIHSS scores were respectively evaluated,and Hcy level was detected in 3 groups on first day of admission and 21st day of treatment,and the clinical efficiency was compared between high-Hcy group and low-Hcy group.Results Hcy levels in high-Hcy group and low-Hcy group decreased significantly on 21st day of treatment.Hcy levels in high-Hcy grouy and low-Hcy group were significantly higher than control group on first day of admission and 21st day of treat-ment,and the increasing range in high-Hcy group was even larger.NIHSS scores decreased,while BI scores increased significantly in 3 groups on 21st day of treatment.NIHSS scores in high-Hcy group and low-Hcy group were significantly higher than control group on first day of admission and 21st day of treatment,while BI scores were lower,and the increasing and decreasing ranges in high-Hcy group were even larger.The overall response rate of low-Hcy group was superior to high-Hcy group.Conclusion Detecting Hcy level can predict the prognosis of patients with ACI,and reduc-ing Hcy level can improve the neural functional defects and life capability of patients.