Chai Hu (Radix Burpleuri), a major ingredient in many traditional Chinese medicine formulas, such as Xiao Yan Wan, is used in the treatment of liver stagnation and spleen deficiency syndrome (LSSDS). The objectives of this study were to examine the effects of Xiao Yao Wan containing Chai Hu on the changes of plasma indices in patients with LSSDS. Fifty-eight cases of LSSDS were randomly divided into two groups: 41 cases in the experimental group were treated with Xiao Yao Wan containing Chai Hu and 17 cases in the control group were treated with Zhi Bai Di Huang Wan for one consecutive month in a single blind design. Before and after treatment, high performance liquid chromatography (HPLC) was applied to determine the changes of plasma norepinephrine (NE), epinephrine (E) and dopamine (DA). Radioimmunoassay was performed to measure the amount of plasma beta-endorphin (beta-EP), adrenocorticotropin hormone (ACTH), estradiol (E2) and testosterone (T), and laser nephelometry was also conducted to measure plasma immunoglobulin A (Ig A) and G (Ig G). Compared to baseline levels, plasma beta-EP was significantly increased (p < 0.01), while E and DA were markedly decreased (p < 0.01) after the administration of Xiao Yao Wan in the experimental group. The other indices did not change. This is the first evidence showing that the effect of Xiao Yao Wan containing Chai Hu on the treatment of patients with LSSDS may be through enhancing plasma beta-EP and decreasing E and DA release. We conclude that Xiao Yao Wan containing Chai Hu regulates nervous and endocrine systems and contributes to the improvement of the clinical status of patients with LSSDS.