Abstract: Effects of environmental conditions on bio-degradation of thifensulfuron was studied in laboratory. Results shown that bio-degradation rate of thifensulfuron was positively related to soil temperature and moisture content, but negatively to the initial concentration of thifensulfuron applied. The higher the soil temperature and the moisture content, the higher the degradation rate;but the higher the initial thifensulfuron concentration, the lower the degradation rate. The degradation rate increased by 2.9 times, when the temperature rose from 5 to 35 ℃. The half-life of thifensulfuron decreased to 2.6 from 7.6 d when the soil moisture content rose from 25% to 75% in saturated water content, but increased from 3.1 to 7.6 d when the initial application rate of thifensulfuron rose from 2.5 to 10 mg·kg^-1.