Abstract: The decline dynamics of different concentration of chlorpyrifos microspheres and chlorpyrifos emulsifiable concentrate(EC) in water,and the sustained toxicity of chlorpyrifos microspheres and chlorpyrifos EC to the 3rd larvae of Aedes albopictus were studied in laboratory.The results showed that the decline rate of chlorpyrifos microspheres was slower than that of chlorpyrifos EC,and the half-life of chlorpyrifos microspheres was longer than that of chlorpyrifos EC.The half-lives of chlorpyrifos microspheres and EC were longer at high concentrations than those of the low concentrations.The half-lives of chlorpyrifos microspheres and chlorpyrifos EC at the dosage of 1.2,12,24 mg/L were (19.4±2.1) d,(27.8±1.6) d,(31.0±1.7) d and (12.8±1.0) d,(16.1±0.9) d,(19.7±1.1) d,respectively.The toxicity of chlorpyrifos microspheres to the 3rd instar larvae of A.albopictus was higher and the duration was longer than that of chlorpyrifos EC.After treatment for 85 days in water,the mortality of mosquito larvae caused by 1.2 mg/L chlorpyrifos microspheres was 76.6%,which was higher than that of the same concentration of chlorpyrifos EC(53.3%).The results suggested chlorpyrifos microspheres had good persistence against mosquito larvae.