Objective The cellular immunity and humoral immunity of the mice with gene knock out Smad3 were studied. Methods The parameters of CD4 ,CD3 ,CD8 ,CD19 ,IgG were detected by FCM and ELISA.Results The parameters of CD8 ,CD4 /CD8 ,IgG of homozygous mice were significant differences between genders. But the parameters of the CD4 ,CD8 ,CD3 ,CD19 ,IgG were lower than those of wild types. Conclusions It is reference value in using the mice lacking Smad3 for the study of disease of human immunity.