Abstract: OBJECTIVE To observe the clinical changes， 5-HT and DA of Zhen Zao Capsule in the treatment of senile patients with yin-deficiency and fire-excess insomnia， thus evaluating the clinical effects and functional mechanism of Zhen Zao Capsule. METHOD 60 cases with yin-deficiency and fire-excess primary insomnia were randomized into the treatment group (30 cases) given Zhen Zao Capsule half an hour before sleep， and the control group (30 cases) treated with Shumian Capsule at the same time. Both groups were given 5 pills per time and one time a day. 4 weeks made up one course of treatment. The two groups were observed every 7 days for one month. Detecting the changes of 5-HT and DA as well as evaluating the clinical effects of two groups. RESULTS The clinical effects of relieving insomnia in both groups were equal (P>0.05). However， in terms of improving the TCM syndromes and effects， the treatment group was superior to the control group (P>0.05). Before and after treatment， 5-HT increased while DA decreased. Amplitude of accommodation in the treatment group was significant than that of the control group， which was of statistical significance (P>0.05). CONCLUSION With significant clinical effects， Zhen Zao Capsule can improve insomnia in senile patients. The treatment mechanism maybe achieved by increasing the 5-HT and lowering DA， thus improving the sleep quality of senile patients.