The study reported the molluscicidal effect of B002 and the synergism of B002 combined with niclosamide. The results showed that molluscicidal rate was 100%,when the concentra- tion of B002 was 6. 25mg/L. But the concentration of B002 was below 0. 39mg/L,there was no molluscicidal effect LD50 of B002 was 0. 8183mg/L. LD,. of niclosamide was 0.082mg/L. But LD50 of niclosamide mixed with 0.4mg/L of B002 declined to 0.0215mg/L. The mollusci- cidal rate wouId be 100% at 0.070mg/L of niclosamide mixed with B002. The molluscicidal effect raised by 3. 28 times. B002 mixed with niclosamide in 0.5: 1, 1: 1,2: 1,the cotoxicity co-effecient (CTC) were 127. 5, 167. 3 and 227.0,respectively It indicated that B002 was a synergist for molluscicidal effect of niclosamide.