Objective:To probe the correlation between the effect of icariin on learning and memory and the level of estadiol（E

2

） in serum in senescence accelerated mouse prone/8（SAMP8）.Methods:10 six-mon-old senescence accelerated mouse resistance 1（SAMR1） and 40 the same age SAMP8 were selected.SAMP8 were divided randomly into 4 groups(model

75 and 150 mg·kg

-1

icariin ig

and 0.2 mg·kg

-1

diethylstilbestrol ig).Then

the effects of icariin administration by oral gavage for 3 months on learning and memory deficits in SAMP8 and SAMR1 were investigated by the Morris water maze test;the level of E

2

in serum in SAMP8 and SAMR1 was determined by radioimmunoassay kit.The mice were sacrificed after ethology test

and the uterus coefficient was calculated. Results: The administration of icariin orally could enhance the learning and memory ability of SAMP8 in Morris water maze test;increase the level of E

2

in serum in SAMP8;create non-significant difference in the uterus coefficient of SAMP8.There was a significant negative correlation between the latency in Morris water maze test and the level of E

2

in serum in SAMP8 analyzed by Pearson correlation coefficient.Conclusions: Icariin could improve the cognitive impairments of SAMP8

and its mechanism may be related to the increase in the level of estrogen in serum in SAMP8.