OBJECTIVE： To study the effects of hypnotic active constituent of Cnidium monnieri （CHC） on sedation and hypnosis， learning and memory， hangover of mice. METHODS： 60 mice were randomly divided into blank control group （2％ Tween 80 solution）， diazepam group （6 mg/kg） and CHC high-dose， medium-dose and low-dose groups （520， 260， 130 mg/kg）， with 12 mice in each group. They were given relevant medicine intragastrically twice a day. The sleep latency and sleep duration， the times of autonomic activities and standing times after sleep， escape incubation period and the number of errors in step through test were observed in each group 1 d after medication. The place navigation test and spatial probe test were conducted 16 day after medication. RESULTS： Compared with blank control group， sleep duration of mice was prolonged in diazepam group and CHC groups while standing times before and after sleep were decreased； in diazepam group， the number of errors was increased before sleep， while activity times was decreased after sleep； escape incubation period was prolonged， while target time was shortened； the ratio of target distance was decreased； escape incubation period of mice was prolonged in CHC high-dose group， with statistical significance （P＜0.05 or P＜0.01）. Compared with diazepam group， sleep duration of mice was prolonged in CHC medium-dose and high-dose group， and activity times after sleep were increased； activity times before sleep were decreased in CHC low-dose group； the number of errors before sleep were decreased in CHC groups， with statistical significance （P＜0.05 or P＜0.01）. Compared with before sleep， escape incubation period of blank control group was prolonged； activity times after sleep of CHC groups were increased while standing times after sleep were decreased； escape incubation period after sleep was prolonged （except for medium-dose group）， with statistical significance （P＜0.05 or P＜0.01）. There was no statistical significance in other indexes （P＞0.05）. CONCLUSIONS： CHC shows sedation and hypnotic effect in mice， but has no effect on learning and memory and doesn’t induce hangover response.