In this study, using of the method of instrumental analysis combined with high performance liquid chroma-tography system under simulated conditions in lab, effect of soil characteristics on the Fomesafen degradation wassystematically studied. Experimental results showed that Fomesafen degradation in tested soil followed the first-or-der kinetics equation, degradation rate of different concentration of Fomesafen was different, degradation rate wasin such order: 100 mg/kg ＞ 50 mg/kg ＞ 150 mg/kg, half-life were 86.64 days, 100.45 days and 119.5 days. The deg-radation rate of Fomesafen was positively correlated with soil temperature, soil organic matter content, and soil mois-ture. When soil moisture capacity increased from 5% to 20%, the Fomesafen decomposition rate was accelerated.Fomesafen degradation rate was gradually accelerated with the increase of temperature, and when the temperaturewas 35 ℃ Fomesafen degradation rate was the fastest. High soil organic matter content was beneficial to enhance thedegradation of Fomesafen, and when organic matter content was 5.5%, degradation rate was the fastest. The degrada-tion rate was inversely proportional to the soil p H value, the degradation rate increased with the decreasing of soilpH value, and when the pH was 5, degradation rate was the fastest.