Abstract: ObjectiveTo observe the effects of reyusan on histologic change of rat with gastrointestinal damp-heat type ulcerative colitis( UC) . Methods: Fifty male SD rats were randomly divided into normal group，model group，high-and low-dose reyusan treatment groups and sulfasalazine( SASP) treatment group.The gastrointestinal damp-heat type UC model rats were established by high fat diet，white spirit damp-heat environment and trinitro-benzene-sulfonic acid.The damage index of rats colon mucosa was observed 15 days after drug administration.Results: Compared with the model group， the damage index of rat colon mucosa in high-dose reyusan and SASP treatment group were significantly low( P 0.01) .The difference of the damage index between low-dose reyusan treatment and model group had no statistical significance( P 0.05) .The damage index of SASP treatent group was lower than that in low-dose reyusan treatment group( P 0.05) ，but higher than that in the model group( P 0.05) . Conclusions: reyusan can significantly improve the colon mucosa damage of rat with gastrointestinal damp-heat type UC and promote ulcer repair，which has good therapy effect