This gager deals with the characteristics of persistance and bound residue of trifluralin in two soils.The results show that (1) dynamics of trifluralin persistent in soils under the tested conditions basically followed the first-order reaction equation(C=C₀^-kr) with a half-life (t) of 15-40 days.The most important facter affecting trifluralin degradation was mtcrobial activity in soil.The water conditions of tested soils would markedly affect persistence of the herbicide as well.In general,the rate of degradation of trifluralin in waterlogged soil was much faster than in aerobic soil.(2) Three metaholites,which were detemined by GC/MS as dealkylative and reductive derivatives of parent,were detected after incubation about two weeks in waterlogged red soil.(3) It was found that trifluralin could be bound by soils in considerable amounts.The capacity of soil binding this chemical varied with soil organic matter content the black soil rich in organic matter coold bind more residue than did the red soil.Waterlogged condition was more favourable to the formation of bound residue than aerobic condition in case of the same soil.(4) GC of the distillation products of soil samples containing boand residues by the high temperature distillation technique show that besides small amount of parent compound,they were mainly composed of metabolites.It seems that this herbicide bound residue in soil was mainly formed through the incorporation of the lowly steric hindered reductive derivatives of parent into soil.