Abstract: Four suspected Bacillus strains were isolated from the intestine of healthy hybrid grouper,which were named as B1,B2,B3 and B4 and studied on the bacterial morphology,biochemistry characteristic,16S rDNA sequences and ectoenzyme-producing analysis.The results showed that four strains were consistent with Bacillus on biochemistry characteristic.Meanwhile,the 16S rDNA sequences of four strains were clustered at similarity levels(≥99%) with Bacillus.Finally,the results showed that four strains were all Bacillus.With the founded of ectoenzyme-producing experiment,four strains all had ectoenzyme-producing ability,such as cellulase,amylase and protease.And B3 strain had higher zymogenicities of cellulase,protease,and amylase than B1,B2 or B4.So this experiment finally selected B3 as a strain with potential probiotic.