The effect of P. americana L. on anxiety and depression-behavior after chronic stress (CS) is still unknown. Here, CS were induced by a combined stimulation of chronic restraint stress, excess failure and improper diet in SD rats. At 15 days after CS, except for normal group and model group, all the groups were continuously administrated P. americana L. (i.g., 400, 200, 100 mg/kg) treatment for 14 days. Anxiety and depression-behavior was determined by sucrose preference test, forced swimming and open field. The contents of cortisol (CORT), adrenocorticotropic hormone (ACTH), adrenocorticotropic hormone-releasing hormone (CRH), interleukin (IL)-4, IL-6, IL-17 and interferon (IFN) -& gamma; were detected by ELISA. 16S rRNA analysis was performed to examine the composition of gut microbiota. Our results indicated that P. americana L. improved the anxiety and depression-behavior. P. americana L. reduced the release of IL6, IL-17 and IFN-& gamma; and increased the release of IL-4. Comparably, remarkably decreased CRH, ACTH and CORT were observed by the treatment of P. americana L. 16S rRNA analysis suggested that Bifidobacterium and sulfate-reducing bacteria may be responsible for improving CS in P. americana L. -treated rats. Collectively, P. americana L. could relieve CS are associated with regulation of intestinal flora.