Objective:To explore the effect of AngiotensinⅣ(AngⅣ) on cognitive function of diabetic rat and the expression of receptor AT4. Methods:Forty SD male rats were randomly divided into the normal group, diabetic model group and AngⅣ treatment group. Streptozotocin-diabetic rat model was established. After 12 weeks of establishment, the learning and memory abilities of rats were tested by the Morris water maze. Then, AngⅣ was injected into the lateral ventricle of AngⅣ treatment group rats once a day for a week,and normal sodium was injected into diabetic model group rats for a week. The learning and memory abilities of rats were tested by the Morris water maze again. The mRNA and protein level of AT4 in hippocampus were detected by RT-PCR and immunohistochemical method. Results:Compared with diabetic model group, the AngⅣ treatment group showed a significant decrease in the mean time of escape latencies(P < 0.05),and a increase in the number of passing the original platform position(P < 0.05). And the expression of AT4 receptor protein and mRNA in hippocampus were decreased significantly(P < 0.05). Conclusion:It was concluded that AngⅣ could improve cognitive ability in diabetic rat,perhaps the decrease of AT4 receptor expression would be one of the mechanism.