Abstract: The degradation dynamics of quinclorac in four kinds of soils (Shandong, Hunan, Sichuan and Yunnan) were studied in laboratory, and the effect of soil pH, moisture, and temperature on degradation was investigated. The results showed that the half-time of quinclorac in the soils was 26.8, 23.9, 35.6, and 32.4 days, and the slowest degradation was in Yunnan soil. The degradation rate of quinclorac in acid soil was slow and the half-time was long. The half-time of quinclorac decreased with increase of soil moisture and environment temperature. The regression equation of half-life with soil pH, moisture, temperature are y=-3.575x+48.425,R²=0.9929; y=-0.2329x+34.1, R²=0.8038; y=-1.11x+57.983, R²=0.9139 respectively.