Objective：To observe the effect of new Maixian powder on the expression of activating transcription factor-4(ATF-4)，C/EBP homologous protein(CHOP)in colon tissues of rats with ulcerative colitis，and investigate its mechanism in treating UC.Methods：Divided 60 SD rats randomly into the normal group，the model group，mesalazine group and new Maixian powder groups of low，middle and high dose，10 rats in each group.UC model was induced by 5%dextran sulfate sodium(DSS)，mesalazine group was given 0.42 g/(kg·d)of mesalazine granules suspension by gavage，while the new Maixian powder groups of low，middle and high dose were respectively given 1.5，3 and 6 g/(kg·d)of new Maixian powder suspension by gavage.Rats in other groups were given saline of the same volume by gavage.Each group continuously received treatment for two weeks.Observed the general situation of rats，evaluated histopathological damage and adopted Western Blot method and RT-PCR method to respectively detect the expression of ATF-4，CHOP protein and mRNA in colon tissues.Results：Compared with those in the normal group，scores of pathological damage of rats in the model group were obviously increased and the expression of ATF-4，CHOP protein and mRNA in colon tissues was increased，differences being significant(P＜0.05).Compared with those in the model group，scores of pathological damage of rats in the mesalazine group and the new Maixian powder groups of low，middle and high dose were obviously decreased，and the expression of ATF-4 and CHOP mRNA in colon tissues was decreased；the expression of ATF-4 and CHOP protein in the mesalazinegroup and the new Maixian powder groups of middle and high dose was decreased；differences were significant(P＜0.05).Conclusion：New Maixian powder has significant effect in treating UC rats，which can inhibit the expression of ATF-4，CHOP protein and mRNA in colon tissues and one of its mechanisms may be reduce cell apoptosis.