Abstract: Objective To investigate the expression of p21^WAF-1 in brain tissue of the acute brain aging rat models, which will provide theory for brain-aging mechanism and clinic prevention and therapy. Methods The rat acute brain-aging model was established by⁶⁰Co radiation, and 5-monthly SD rats as the control group. The learning and memory of rats ability was determined by Y type labyrinth, and the antioxidant and lipid peroxidative injury of rats were measured by SOD and MDA in blood. With the in situ hybridization, the expression of p21^WAF-1 in hippocampal neuron was measured. Results The learning and memory ability of brain aging rat was decreased with Y type labyrinth. The blood’s SOD in brain-aging model was significantly lower than that of the control, the blood’s MDA in brain-aging model was markedly higher than that of the control. Over expression of p21^WAF-1 was found in hippocampus, cortex, in hypothalamus and corpus striatum secondly, and in cerebellum est, the expression of p21^WAF-1 were found in cone cells of cortex and hippocampus, in purkinje cells of cerebellum；the expression of p21^WAF-1 were negative in cerebellum of control group, and the expressions of p21^WAF-1 were found in other different brain regions in control group, but lower and weaker. Conclusions The simple and easy acute brain-aging model was established.Over expression of p21WAF-1 may maintain the character of senile neuron.