To observe the expression of TPH2 and IDO1 in hippocampus of rat with syndrome of liver depression and spleen deficiency, and to explore the regulating effect of xiaoyaosan. Methods:Male SD rats were randomly divided into 4 groups：normal group, model group, xiayaosan group and fluoxetine group, each including 6 rats. The liver depression and spleen deficiency model was established by chronic immobilization stress for 21 days. The expression of TPH2 and IDO1 were detected by Fluorescent quantitative PCR and Western-blot method. Results:The mRNA expression of TPH2 in hippocampus of model group decreased significantly compared with the other groups (P<0.05); xiaoyaosan and fluoxetine could increase the TPH2 mRNA expression. The mRNA expression of IDO1 in hippocampus of model group increased significantly (P<0.01); xiaoyaosan and fluoxetine had the down-regulatory effect on IDO1 mRNA expression (P<0.01), which is more obvious in xiaoyaosan group. The protein expression of TPH2 in normal group was higher than the other groups (P<0.01), which of xiaoyaosan group was higher than model group (P<0.05); the protein expression of IDO1 in model group increased significantly compared with the other groups (P<0.01). Conclusion:The expression of TPH2 decreases and IDO1 increases in liver depression and spleen deficiency model rats, and xiaoyaosan has a therapeutic effec by regulating TPH2 and IDO1 in hippocampus to influence the content of 5-HT.