Objective To study the effect of increased brain edema and the expression of A-β protein in the hippocampus on learning and memory functions of rats after subarachnoid hemorrhage(SAH).Methods We randomly divided 48 adult SD rats into model group and sham-operation group,each with 24.The model of SAH was established by Bederson method.Morris water maze was used to detect the spatial learning and memory functions of the rats at day 3,7,14 and 28 after modeling;A-β protein expression in the hippocampus was detected by the immunohistochemical method.Results At the corresponding time points after modeling,the latency of escape was significantly longer in model group than that in sham-operation group(P＜ 0.05).However,the two groups did not significantly differ in A-β protein expression at day 3(P＞0.05);A-β positive cell counts increased significantly at days 7,14 and 28(P＜0.05).Conclusion Memory impairment of learning machine,edema of brain tissue,and the increase of A-β protein expression may induce cognitive dysfunction after SAH.