Abstract: We analyzed the effect of Bacillus cereus (algicidal bacteria CZBC1) on microalgae community in shrimp aquaculture water by method of experimental ecology. According to the algicidal bacteria amount,we set Group J0 (0 CFU · mL^-1),Group J3 (3.0×10³ CFU · mL^-1) and Group J5 (3.0×10⁵ CFU · mL^-1) with three parallels. The initial dominances of Oscillatoria chlorine and Oocystis borgei,the dominant species in water,were 64.14% and 16.42%,respectively. The results show that the dominance of O.chlorine in Group J0 was significantly higher than those in Group J3 and Group J5 after 15-day culture (P<0.01),and their dominances were 81.86%,16.7% and 14.6%,respectively. While the dominance of O.borgei in Group J0 was significantly lower than those in Group J3 and Group J5 (P<0.01),and their dominances were 3.13%,32.42% and 47.14%,respectively. The mortality of shrimp in Group J0 was significantly higher than those in Group J3 and Group J5 on the 6^th day (P<0.01),which were 82.2%,46.7% and 31.1%,respectively. Furthermore,the mortality in Group J0 was also higher than those in Group J3 and Group J5 on the 15^th day. The results indicate that algicidal bacteria CZBC1 can inhibit the growth of O.chlorine (Cyanophyta) effectively,which helps occupy the ecological advantage for O.borgei (Chlorophyta),providing better water environment for the growth of shrimp.