Using fresh unpolluted cole as the material and orthogonal design trials were carried out on the degradation of methamidophos on vegetable and its effect on the quality of cole. The result showed that Calcium Hypochlorite had strong degradation effect on pesticide residues and the appropriate condition was as follows: C=300mg/L t=20min pH=4,and the rate of pesticide residues is 28.27%;when C=300mg/L,t=10min,pH=4 ,the rate of pesticide residues was less than 33.64%.