Objective To observe the tumor inhibitory effect and its mechanism of Fuzheng Xiaoai Formula（formula for supporting the right-qi a nd resisting tumor） on Lewis lung cancer（LLC） mice.Methods Sixty C57BL/6J mice were used to establish LLC models and they were random ize d into the cancer model group

cisplatin（CTX） group

Chinese medication group a nd co mbination group

with 15 in each.The CTX group was treated with intraperitoneal injection of 0.2ml（4mg/ml） CTX solution 72 hours after vaccination.The Chine se medication group was treated with intragastric administration of 0.4ml（2g/m l） Fuzheng Xiaoai Formula 5 days before modeling.The combination group was treated with both Fuzheng Xiaoai Formula and CTX.The cancer model group was given 0.4ml of normal saline intrag astri c ally.The intragastric administration repeated once daily for 12 days.The survi val status and the growth of transplanted tumors were observed.The weight of tu mor and thymus was weighed.The tumor inhibitory rate and thymus index were calc u lated.The expression of CD44 was detected with immunohistochemical method.Results Comparing with the cancer model group

the tumor w eight decreased significantly i n other groups（P<0.01）.The tumor weight in the combination group was sign ifica ntly lower than that in the CTX group（P<0.01）.The tumor inhibitory rate o f the CTX group

Chinese medication group and combination group was 83.97%

55.71% an d 87.23% respectively.Comparing with the cancer model group

the thymus weight in th e CTX group and combination group decreased significantly（P<0.05 or P< 0.01）

and the thym us index decreased significantly in the CTX group（P<0.01）.Comparing with the C TX group

the thymus weight in the Chinese medication group increased significan tly（P<0.01）

and the thymus index in the combination group increased signi fican tly（P<0.05）.The degree of CD44 expression in the combination group was th e lowest with statistical significance as compared with that in CTX group（P <0.05）.Conclu sion Fuzheng Xiaoai Fo rmula could increase the effectiveness of chemotherapy drugs

improve the sensit ivity of tumor cells to the immune system and anti-cancer drugs

down-regulati ng or reversing the expression of CD44 and play a role in tumor inhibitory and anti-metastasis.