Abstract: An efficient method for the determination of cyantraniliprole and its metabolite J9Z38 residues in maize plant and soil were established using ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). The fate of cyantraniliprole and J9Z38 in maize plant and soil after seed treatment was also evaluated. The target compounds were extracted with acetonitrile, pretreated using QuEChERS method and analyzed by UPLC-MS/MS. The mean recoveries of cyantraniliprole and J9Z38 at three spiked levels (0.01, 0.1 and 1 mg/kg) ranged from 81% to 103%, respectively, with relative standard deviations both less than 10.1%. The results demonstrate the concentrations of cyantraniliprole and J9Z38 have a good linear relationship with the corresponding peak area in the range of 0.1-50 μg/L, with dertermination coefficient (R² > 0.999), and limits of quantitation were 0.01 mg/kg. The dissipation dynamics of cyantraniliprole and J9Z38 were both in line with the first order kinetic equation. The half-lives of cyantraniliprole in maize plant and soil were 8.3 and 8.2 d (in spring), and 3.9 and 4.5 d (in summer), respectively. All the above observations indicate that the established analytical method is sample, sensitive, highly efficient, and suitable for monitoring the residues of cyantraniliprole and its metabolite J9Z38 in maize plant and soil.