Abstract: To apply chlorpyrifos scientifically and safely in vegetable facility cultivation, the residue dynamics of 48% chlorpyrifos EC on Brassica chinensis grown under greenhouse, network and open field conditions were compared by using the methods of laboratory test and field experiment according to Guideline for Pesticide Residue Testing. The samples were extracted ultrasonically with acetonitrile, cleaned up by florisil solid-phase extraction column and determined by gas chromatograph with electronic capture detector. The average recoveries of chlorpyrifos on Brassica chinensis were 84.6%-98.8% with relative standard deviations (n=3) ranging from 3.7% to7.6% in the spiked level of 0.01-0.5 mg/kg。The limit of detection and quantification was 0.005mg/kg and 0.01mg/kg, respectively. The field experiment results showed that when sprayed once at effective constituent concentration of 1152g/hm2, the original residues of chlorpyrifos on Brassica chinensis from different cultivation modes were relatively higher, and their residual dissipation accorded to the first order kinetic equation model with half life from 1.56 to 1.71d. Chlorpyrifos is classified as an easily degraded insecticide and the dissipation velocity was related to its cultivation pattern. The dissipation rate of chlorpyrifos on Brassica chinensis followed the order of open field＞network＞greenhouse. When sprayed with 576-1152g/hm2 one time or twice at 7 days intervals, the final residues of chlorpyrifos on Brassica chinensis under different cultivation patterns were all lower than the MRL of China (0.1mg/kg) at 14 days after last application. It is recommended that when applied on Brassica chinensis under greenhouse, network and open field conditions to control insects and mite pests, the pre-harvest interval of 48% chlorpyrifos EC should be set 14d and sprayed one time or twice at the dosage no more than 1152 g/hm2. The Brassica chinensis harvested at this time is safe to eat.