Objectives: This study was perfomed to investigate the antioxidant activity and serotonin activity of Gami-guibi-tang on P815 Mast Cell. Methods: The effects of Gami-guibi-tang on activation of TPH-1 mRNA and AAADC mRNA in P815 mast cell were investigated. The effect of Gami-guibi-tang on content of serotonin in P815 mast cell was investigated. The effects of Gami-guibi-tang on activation of DPPH radical scavenging and SOD in P815 mast cell were investigated. Results: 1. The Gami-guibi-tang increased SOD activity and DPPH radical scavenging activity. 2. The Gami-guibi-tang increased the intracellular concentration of serotoninin 60 ${mu}g/ml$, 80 ${mu}g/ml$ experiment group. 3. The Gami-guibi-tang increased menaingful the manifestation TPH mRNA. 4. The manifestation of AAADC and MAO mRNA have not made menaingful changes on Gami-guibi-tang. Conclusions: This experiment shows that Gami-guibi-tang had significant anti-oxidative effect. And Gami-guibi-tang increased the intracellular concentration of serotonin. Therefore, Gami-guibi-tang can be used by the medication of major depression disorder. But Study on mechanism of increased serotonin and clinical research of Gami-guibi-tang is suggested for future research.