Abstract: This study was conducted to explore the effects of Yujin powder (YJP) on SIgA and inflammatory cytokines in ileal and colonic mucosa of Large Intestine Dampness-heat Syndrome (LIDHS) rat. Forty Wistar rats were randomly divided into 4 groups:normal control, LIDHS model, self-healing and YJP treatment group, with 10 rats in each group. The rat model of LIDHS was established through setting such complex factors as high-sugar and high-fat diet, improper diet, high temperature and high humidity environment, drinking and intraperitoneal injection of Escherichia coil to imitate the inducing conditions of LIDHS. After the model being successfully established, the rats of YJP treatment group were treated with YJP for 5 days. And then we collected ileum and colon, made histopathological slices and observed the pathological changes of ileum and colon. Mucous SIgA and tissue TNF-α, IL-1β, IL-6, IL-10, IL-17 and IL-23 in ileum and colon were detected by ELISA method. The results showed that in model rats, the ileal and colonic mucosal epithelium cells showed degeneration, necrosis and exfoliation, the integrality of epithelium was destroyed; and there were inflammatory cells infiltration. In YJP group, mucosal epithelium regenerated, the integrality was recovered, the continuity was good, epithelium cells have a regular arrangement, and inflammatory cells infiltration obviously decreased. The contents of mucous SIgA in ileum and colon in LIDHS model group were significantly higher than those in normal group (P<0.05); those in YJP treatment group were both significantly lower than those in self-healing group (P<0.05). The contents of pro-inflammatory cytokines TNF-α, IL-1β, IL-6, IL-17 and IL-23 in ileum and colon tissue were significantly or extremely significantly higher than those in normal group (P<0.05 or P<0.01). The contents of anti-inflammatory cytokine IL-10 were significantly or extremely significantly lower than those in normal group (P<0.05 or P<0.01). The contents of above inflammatory cytokines in ileum tissue in YJP treatment group were significantly different from those in self-healing group (P<0.05); the contents of TNF-α, IL-10 and IL-23 in colon were significantly different from those in self-healing group (P<0.05); the contents of IL-1β, IL-6 and IL-17 were extremely significantly different from those in self-healing group (P<0.01). It is demonstrated that ileal and colonic mucosal immune homeostasis of LIDHS model rat was destroyed, which manifested as hypersecretion of SIgA and secretion disorder of inflammatory cytokines. The treatment of YJP could back-regulate this phenomenon.