Objective To observe the efficacy and safety of venlafaxine on cognitive function in patients with post stroke depres-sion(PSD) .Methods 72 patients of cognitive dysfunction with PSD were selected and randomly divided into observation group and control group with 36 cases in each .The control group was treated with therapy for acute stroke .The observation group was treated with venlafaxine based on the treatment of control group .After 12 weeks of treatment ,the mini mental state examination(MMSE) , the Montreal cognitive assessment scale(MoCA) and activities of daily living scale(ADL) were used to evaluated the efficacy of the two groups before ,fourth weeks after and twelfth weeks after the treatment .The scores of the two groups were compared .The oc-currence of adverse reaction of the observation group was recorded .Results After 4 weeks treatment of the observation group ,the MoCA was (18 .52 ± 4 .37) .MMSE score was (20 .61 ± 4 .85) ,which were significantly higher than before treatment .And the ADL score was (35 .27 ± 4 .75) ,significantly lower than before treatment(all P<0 .05) .After 12 weeks of treatment ,the MoCA score of observation group was (20 .14 ± 5 .26) .MMSE score was (22 .46 ± 4 .59) .Which were all significantly higher than those of control group .While the ADL score was (29 .85 ± 5 .07) ,significantly lower than the control group(all P<0 .05) .The observation group with 2 cases had mild gastrointestinal discomfort ,2 cases with dizziness .Conclusion Venlafaxine can improve cognitive function in patients with post stroke depression .It can significantly improve patients′self-care ability and is safe .It can be further applied in the clinic .