Abstract: To investigate effects of Lactobacillus rhamnosus on growth characteristics and antioxidant indexes of tilapia in an aquaponics system, an experiment was established with three groups, tilapia monoculture group（T₁）, tilapia-water spinach group（T₂）, and tilapia-water spinach-Lactobacillus rhamnosus group（T₃）．T₁ and T₂ groups were fed with basal diets, while T₃ group was fed with basal diets supplemented with 1×10⁸ CFU/g Lactobacillus rhamnosus．Results showed that end-body length, average weight gain rate, end body weight, and average growth rate of tilapia treated with T₃ group were significantly higher than those of T₁ group（P<0.05）．Total protein（BCA）content in tilapia serum, activity of glutathione peroxidase（GSH-PX）and catalase（CAT）in tilapia serum and liver in T₃ group were significantly higher（P<0.05）than those in T₁ and T₂ groups．Adding Lactobacillus rhamnosus to feed could improve tilapia growth performance．Optimizing diversity of intestinal flora of tilapia in aquaponics system could further improve antioxidant capacity of liver and serum to scavenge free radicals．And metabolic level and immune function of fish could be improved to a certain extent, which would ultimately improve production efficiency of aquaponics system．