Abstract: Objective To evaluate the application of serum Hcy in treatment of atherosclerotic cardio-cerebral disease and diabetes. Methods Relationship between the levels of serum Hcy and folate,VB 12,Glu,CH,Tg,ApoA,ApoB,HDL-CH,LDL-CH,UN,Cr,Ua,Lpa,Gruc,Cys in 327 patients with atherosclerotic cardio-cerebral disease or diabetes and 67 controls was retrospectively analyzed and compared. Results The serum Hcy level was negatively correlated to the levels of serum folate,VB 12,ApoA,HDL-CH,and positively correlated to the levels of serum UN,Cr,Ua and Cys,but no significantly correlated to Glu,CH,Tg,Apoa,ApoB,HDL-CH,LDL-CH.The level of serum Hcy in patients with atherosclerotic disease and diabetes was much higher than that in the control group. Conclusion Hyperhomocystinemia is a risk factor for atherosclerotic diseases.Supplement therapy for hyperhomocystinemia with folate and VB12 can reduce the serum Hcy level in patients with atherosclerotic disease and diabetes.