Abstract: Objective: To investigate the regulative mechanism of oxymatrine on the expression of toll-like receptor 9(TLR9) and nuclear factor-κB(NF-κB) at mRNA level in colonic tissue of rats with ulcerative colitis(UC).Methods: Seventy-five adult SD rats with SPF grade were divided into 5 groups randomly:control group,oxymatrine treatment group,mesalazine treatment group,oxymatrine and mesalazine combined treatment group,and model group.One week after the experiment,three rats in each group were randomly selected and executed for observing the histological changes of colonic tissue.On the 15th day the remaining rats were executed to detect the expressions of TLR9 and NF-κB at mRNA level in colonic tissue by reverse transcription polymerase chain reaction.Results: The mRNA expression level of TLR9 in UC model rat colonic tissue were higher than that in drug treatment groups and control group(P<0.01).In the treated groups,the lower expression of NF-κB at mRNA level was shown in oxymatrine+mesalazine combined group than that in model group,oxymatrine group and mesalazine group alone,which had the statistical differences(P<0.05 to P<0.01),but there had no difference between the oxymatrine group and mesalazine group(P>0.05).Conclusions: Oxymatrine could regulate TLR9 and NF-κB expressions at mRNA level in inflammatory colonic tissue,thereby inhibited the inflammatory response of UC.The combined treatment of oxymatrine and mesalazine had a better effect on blocking the TLR9 and NF-κB pathway to alleviate the inflammatory reaction in UC than oxymatrine or mesalazine treatment alone.