Objective To research the effect of Tiaohe Ganpi Decoction on treating insomnia. Methods To observe the effects of Tiaohe Ganpi Decoction on the sleep of mice induced by pentobarbital with threshold and subthreshold doses by recording the time of sleep and the rate of falling asleep; The rat models of insomnia were induced by injecting PCPA,which were observed on the content of 5-HT after. Results Tiaohe Ganpi Decoction could significantly prolong the sleep time of mice within threshold dose（ P < 0. 01）,and the sleep duration（ P < 0. 01）; the rate of falling asleep on mice could be significantly increased within subthreshold dose; and the content of 5-HT in the insomnia rat brain could be also increased（ P < 0. 05）. Conclusion Tiaohe Ganpi Decoction has some certain effect on treating insomnia.