Concentrate liquid of Bacillus firmus PC465 was mixed thoroughly with the feed materials to produce granules at different doses of 106, 108 and 1010CFU/g dry matter; or freeze-dried and added to feed at a dose of 107CFU/g dry matter. Three feeding regimes were set up at feeding frequencies of “1+1”interval, “4+3”interval and continuous feeding. The effects of feeding B. firmus PC465 on growth and expression of STAT gene in Litopenaeus vannamei were studied at different adding doses and feeding frequencies. By adding PC465 at doses of 106, 108, and 1010CFU/g, significant improvements were observed in the growth rates and STAT gene expression levels in the lymphoid tissue of L. vannamei (P<0.05). The effect was the most significant in the continuous feeding treatment. The finding in this research may provide reference to the healthy aquaculture of shrimp.