Abstract: 【Objective】 This project aims to clarify the residual degradation dynamics of metolachlor in sugar beet and planting soil. 【Method】 QuEChERS-GC/MS method was used to study the effects of different concentrations of S-Metolachor in different soil depths and sugarbeet. 【Results】 The results showed that the S-Metolachorresidue was linear in the concentration range of 0.01-1.0 mg/L with a correlation coefficient of 0.999 4.The minimum detection limit was 0.001 mg/kg; the average recovery was 84.81-110.45%, relative standard deviation (RSD, n=3) was between 1.36% and 9.0%.The degradation of S-Metolachorresidue in 0-5, 5-10, 10-15 cm soil and sugar beet in 1,296, 1,944, 3,888 g.a.i/hm², following the first-order kinetic equation.The residue in different depth soil increased with the increase of concentration, and decreased with the extension of time.The half-life of different application concentration in different depth soil was 9.12-17.77 d.The higher the application concentration, the slower the degradation rate.The residual amount and degradation rate in sugar beet were lower than that in soil, and the half-life was slightly higher than that in soil.The half-lives of three concentrations in sugar beet were 19.25 d, 26.65 d and 32.85 d, respectively. 【Conclusion】 The degradation rate of S-Metolachlor in soil and sugar beet can reach 90% when 1,296 g.a.i/hm² and 1,944 g.a.i/hm² are applied, and is lower than 80% when the dosage of S-Metolachlor is 3,888 g.a.i/hm².From the perspective of degradation rate, S-Metolachlor is easy to degrade in soil and sugar beet, which belongs a kind of degradable pesticide.