Abstract: In order to evaluate the residue behavior and dietary exposure risk of chlorfenapyr and its metabolite tralopyril applied to mustard, the supervised residual trial of chlorfenapyr in mustard were carried out in Shanxi, Beijing, Jilin, Henan, Anhui and Guizhou Provinces in China. A rapid and simple analytical method for determination of chlorfenapyr residues using GC-MS/MS and for tralopyril residues using UPLC-MS/MS in mustard was developed. The final residues and dissipation dynamics were studied, and the long-term and short-term dietary intake risks of the two pesticides to different Chinese populations were evaluated. The results showed that the average recoveries of chlorfenapyr and tralopyril in mustard samples at three spiked levels from 0.01 mg/kg to 30 mg/kg were 89%-105% and 97%-104%, with the relative standard deviation (RSD) ranged from 2% to 4% and 1% to 3%, respectively. The limits of quantification (LOQs) of the two analytes in mustard root and mustard leaf were all 0.01 mg/kg. The dissipation dynamics of chlorfenapyr in mustard leaves accorded with the first-order reaction kinetic equation, and the half-life was 4.2-5.9 days, while the dissipation dynamics of tralopyril could not be fitted with the first-order reaction kinetic equation. The suspension concentrate of chlorfenapyr was sprayed twice at a 5-days interval and a dosage of 105 g a.i./hm² with a pre-harvest sampling interval of 14 days. The long-term dietary intake risk assessment at 97.5% food consumption showed that the contribution rate of mustard leaf residues to the ADI for children aged 3-5 and for the general population was 0.49% and 2.47%, respectively. This indicated that the chronic dietary intake risk of chlorfenapyr and its metabolite through mustard was very low. However, the short-term dietary intake risk assessment showed that the chlorfenapyr in mustard leaves had an unacceptable acute dietary intake risk for both Chinese children aged 1-6 years and the general population. The risk of acute dietary intake for children aged 1-6 years was much higher than for the general population. Changing of the pesticide application methods will lead to differentiated risk assessment results. Increasing the application dose or application times will lead to a higher acute dietary intake risk. Therefore, it is suggested to reduce the level of acute dietary intake risk by prolonging of the pre-harvest interval.