Abstract: AIM: To study the effects of diferent doses of Diazepam on mice spontaneous motor activity,learning and memory function. METHODS: 120 Kun-ming mice were randomly divided into 4 groups. NS Group was given by hypodermic injection normnal saline with the doseof 10 mL/kg; the other 3 groups (groups Do.5，D1.o and D2.o) were given by intraperitoneal in-jection diazepam with the different doses of 0.5mg/kg,1.0mg/kg and 2.0mg/kg respectively. The mice were then conducted to take step-down test and steprthrough test to evaluate the efects of Diazepam on leaming and memory function by studying the latency of reaction and the number of errors in its perfomance. RESULTS: Compared w ith NS Group, Diazepam reduced the number of autonomic activities with dose dependently,shortened the latency of eaction and increased the number of errons of stepdown test and step-through test. CONCLUSION: Diazepam can decrease the mice spontaneous motor activity， restrain the leaming and memory function of mice，and the effects disappear quickly after 3 days.

Key words: Diazepam, learming and memory, step-down test, step-through test, spontaneous motor activity, mice