Objective To evaluate the effect decreasing of the incidence of endodontic interappiontment pain(EIP) bylocal injection of 5mg triamcinolone acetonide. Methods 5mg triamcinolone acetonide was injected submucosally at apicalregion of 110 teeth with asymtomatic pulp necrosis after the first root canal therapy, then observing the incidence of EIP andcompared with control group. Result Analysis with statistics the difference of incidence of EIP of the two group was significant(P <0.01 ). Conclusion The incidence of EIP can be reduced after 5mg triamcinolone acetonide Local injected.