Abstract: The hydrolysis of Aldicarb ( AS ) and its toxic metabolites, Aldicarb sulfoxide ( ASO ) and Aldicarb sulfone ( ASO2 ) in aqueous media of pH 5.00, 7.00 and 9.00 were studied. Results showed that AS, ASO and AS02 were relatively stable under neutral and acidulous aqueous media. The hydrolysis rates of three compounds increased as the pH of media increased. At the temperature of 15℃ the half lifes of AS, ASO and ASO2 in the aqueous media of pH 5.00, 7.00 and 9.00 were 627, 510 and 354 days ( for AS ), 330, 267 and 192 ( for ASO ), and 1411, 399 and 100 days ( for ASO2) , respectively.