Abstract: Objective To study the inhibitive effect of B7-H3 on the growth of Lewis lung carcinomas(LLC) cell. Methods Forty C57BL/6 mice were subcutaneously inoculated with LLC cells suspension (1×107/ml) in the right armpit.The tumor-bearing mice were randomly divided into four groups：empty plasmid (as control)，docetaxel，B7-H3 and docetaxel+B7-H3 were injected subcutaneously around the tumor.Tumor sizes were valued at the first，third，seventh and fourteenth day after injection.B7-H3 expression was detected by immunohistochemistry and Western blot.The level of serum IL-12 was detected by ELISA. Results Tumor was inhibited by docetaxel and B7-H3.The inhibitory rates in the groups of docetaxel，B7-H3 and docetaxel+B7-H3 were 32.98%，28.59% and 45.95%，respectively.The apoptosis rate of tumor cells after treatment was significantly increased (P<0.01).B7-H3 expression in tumor tissue decreased in the groups of B7-H3 and docetaxel+B7-H3，although the difference was not significant (P> 0.05).The level of serum IL-12 increased in the groups of B7-H3 and docetaxel+B7-H3 than that in control group (P<0.05). Conclusion B7-H3 can inhibit the growth of murine Lewis lung cancer cell，and promote cytotoxic T cells induced by IL-12 leading to anti-tumor immune response.