Objective：To study the effect of MK-801 on the learning and memory function of Alzheimer’s disease model rats and Neuronal pycnosis、the expression of Aß. Methods：32 male SD rats were divided into model (STZ)+MK-801, sham operated+MK-801, sham operated + saline，model (STZ)+saline groups，randomly．The models of Alzheimer’s disease were created by intracerebroventricular injection of STZ．MK一801 or saline were administered to the 4 groups . All groups were tested on Morris water maze test on Day10 and Day 30. The pycnosis rate was observed by HE staining and the Aß positive neuron rate by immunohistochemistry staining at last. Results：AD model rats who were IP Mk-801 got shorter latencies ,less passing through platform times、redused pyknosis rate and Aß positive neuron rate ,compared to AD model rats who were IP saline 30 days later, this change was statistically significant (P < 0.05);Comparing the difference between the AD model group and sham operated group (that is, to remove the influence of head trauma surgery)：intraperitoneal injection of MK - 801 reduced latencies gap, increased passing through platform times gap and redused pyknosis rate and Aß positive neuron rate gap compared to saline, this change was statistically significant (P < 0.05). Conclusion: intraperitoneal injection of MK-801 improved the learning and memory capabilities of AD model rats ,reduced neuronal pyknosis and deposition of Aß.