The bacterial strain of 4 kinds of application bacteria carried on this study, including Rhodobacter sphaeroides, Bacillus subtilis, Lactobacillus acidophilus , Enterococcus faecalis ,etc. and will defined protective effect in tilapia, Oreochromis nilotica. The result showed that growth rate of SG , AG , FCR value of 4 kinds bacterial strain in diet groups better than to control group; Bacterial challenged test showed , 24h LC50 of 4 kinds of application bacteria all <105cfu/fish, and showed good result of lysozyme , superoxide anion , SOD ,etc. than to conrol group.