Abstract: The main immune indexes of hybrid tilapia (Tilapia nilotica ♀×T.aurea ♂) were measured every two weeks. The 0.05 and 0.10 mg · L^-1 sodium dodecyl benzene sulfonic (SDBS) had not affected the numbers of NBT-positive cells and content of IgM. The 0.40 mg · L^-1 SDBS significantly reduced the numbers of NBT-positive cells and content of IgM in eighth week. The 0.70 mg · L^-1 SDBS significantly reduced the numbers of NBT-positive cells and content of IgM in sixth week. The 0.10 mg · L^-1 SDBS significantly reduced the numbers of NBT-positive cells and content of IgM in fourth week. Mortality of hybrid tilapia after injection of Aeromonas hydrophila (0.40, 0.70 and 1.00 mg · L^-1 SDBS) was higher than the control. These results indicated that low concentration of SDBS (0.05 and 0.10 mg · L^-1) did not affect the immune function of hybrid tilapia, but the higher concentrations of SDBS (0.40, 0.70 and 1.00 mg · L^-1) will apparently reduce the immune function of hybrid tilapia along with time changed.