Abstract： Objective To explore the relationship between the homocysteine(Hcy) level and cerebral watershed infarction(CWI).Methods The levels of Hcy,folate,and vitamin B12 in 58 patients with cerebral watershed infarction( Test Group) were measured and compared with 56 healthy controls (Control Group ).Results Compared with the control group,the levels of Hcy,folate,and vitamin B12 in test group had statistically significant difference (t =2.013,2.842,3.051,P ＜ 0.05 ).Hcy,folate,and vitamin B12 in different CWI subgroup had no statistically significant difference( P ＜ 0.05 ).Conclusion Hcy may be one of the main reasons of CWI.