Abstract: OBJECTIVE To observe the influence of Tongxie Yao Fang on the ERK1 and ERK2 gene expressions of colonic mucosa in rats with ulcerative colitis （UC）， and to identify its underlying mechanism of action.METHODS Experimental animals were divided into six groups and prepared by means of TNBS/ ethanol enema to observe their morphological injury and damage with the naked eyes， and to detect ERK1 and ERK2 gene expressions by means of RT-PCR with ERK1 and ERK2 being the observation targets.RESULTS Inflammation and ulceration on the colonic mucous membrane of rats were observed with naked eyes， which suggested a successful modeling compared with the control group (P<0.05). The relative expression amount of ERK1 and ERK2 of colonic tissues of rats in the model group was higher than that of the blank group （P<0.05）; after treatment， compared with the model group， the relative expression amount of ERK1 and ERK1 in the prescription high- and moderate-dose groups were increased （P<0.05 and P<0.01）.CONCLUSION Tongxie Yao Fang can promote the relative expression amount of ERK1 and ERK2 of colonic tissues of rats with UC， which suggests the therapeutic effects of the prescription are probably related to the activation of ERK signal transduction pathway.