Both field and labor atory experiments of different soils show that the hysteresis phenomenon of soil water movement existed in almast all kinds of soils.However,it has a greater effect on water flow in linht soils.The maximum soil water content due to hystersis was about 20 %(vol./vol)in medium and find sandy soils,11.l% in.silty soil,but only 3% in silty clayey doam.At present,four differenr approaches——domain theory algorithm,linear alborithm,interpolation algorithm and analytical algorithm are commonly introduced in considering hysteresis in numerical simulation of water flow.It is shown that the linear algorithm has the advantages of simplicity,ease and sufficient accuracy,parficularly in the higher order scaning process.