Objective To observe the efficacy of folic acid combined with mecobalamine for the treatment of vascular mild cogni-tive impairment (VMCI) in patients with cerebral small vessel disease (SVD) and hyperhomocysteinemia(Hcy) .Methods A total of 84 VMCI patients with cerebral small vessel disease and Hcy were randomly divided into combination group and control group . Two groups received conventional therapy for 6 months .Besides ,the combination group received folic acid combined with mecobal-amin .The level of plasma Hcy and ADAS-cog score were observed before and after 3 months and 6 months treatment .Results Af-ter treatment ,plasma Hcy significantly lower in the combination group (P<0 .01) ,whereas it did not show any improvement in the control group .ADAS-cog scores in combination group decreased compared with that of before treatment ,but there was no statisti-cally significant difference after 3 months treatment(P>0 .05) .However ,after 6 months treatment ,the ADAS-cog scores decreased obviously than that in the before treatment group (P<0 .05) .ADAS-cog scores in control group increased compared with before treatment ,but there was no statistically significant difference in after treatment (P>0 .05) .After 3 months treatment ,there was no significant difference on ADAS-cog score between combination group and control group (P>0 .05) ,however ,there had significant difference between the two groups after 6 months treatment(P<0 .05) .Conclusion The level of plasma Hcy could be reduced by adding folic acid and mecobalamin .Treatment of hyperhomocysteinemia may delay the progression of vascular cognitive impairment w hich caused by cerebral small vessel disease .