Using instrument determination, effect of environmental conditions on leaching regulation of mesotrione in the soil was systematically studied. The results showed that leaching of different concentration of mesotrionewere different under different rainfall, in different kinds of soil with different organic matter and different additives.As concentration of mesotrione and rainfall increased, it leached deeply in the soil. With the increase of organic matter content in the soil, the absorbability of soil increased, the determined concentration gradually reduced. Differentadditives were added in different soil, with increase of concentration of mesotrione, the determined concentration insoil gradually reduced.