Objective:To investigate the effects of Anchang Decoction on intestinal microflora and faecal calprotectin (FC) in rats with severe ulcerative colitis based on probiotics.Methods:Totally 50 rats were taken to prepare a model of severe ulcerative colitis. The rats who successfully modeled were divided into model group, Anchang Decoction low-, medium-, high-dosage groups, Lizhu Changle group, and mesalazine group, with 5 rats in each group. Another 6 rats were set and the blank group. Lizhu Changle group received Lizhu Changle suspension (containing 50 million live bacteria/ml) for gavage; Anchang Decoction low-, medium-, high-dosage groups received Anchang Decoction 1, 5, 10 ml/(kg·d) for gavage; Mesalazine group received Mesalazine suspension (10.5 mg/100 g) for gavage. Rats in the blank group and model group were gavaged with the same volume of normal saline for 7 days. Body mass and disease activity index (DAI) before and after administration were measured. 16s rDNA of lactobacillus and bifidobacterium in feces of rats was detected. FC content of rats was detected by ELISA.Results:Compared with the model group, the weight of rats in each administration group increased ( P<0.05), DAI score decreased ( P<0.05), and the level of calprotectin in feces decreased ( P<0.05), and there was no significant difference in the levels of lactobacillus and bifidobacterium in each administration group ( P>0.05). Conclusion:Anchang Decoction can improve the intestinal micro-ecology by regulating the level of calprotectin in rats with severe ulcerative colitis, thereby playing a therapeutic role.