Abstract: In order to study residue,half-life period and safe crop period of dimethoate,omethoate,methamidophos in vegetable,we selected green mustard planted in the suburb of Nanchang city as samples,and analyzed residue contents in 0.5h、1d、2d、4d、7d、11d、17d respectively after spraying the three pesticides.The results showed that the half-life period is 2.19d,3.29d and 3.60d respectively,and the safe crop period of dimethoate was shorter than the others in single spaying.So,dimethoate was safer and suitable for the use in the vegetable,but the green mustard must be on sale after 8 days,and 10 days in best.The omethoate and methamidopho belonged to high-persistent pesticide,and the safe crop period of them are long.Therefore,omethoate and methamidophos were forbidden to use in green mustard.