Abstract: Preferential flow is applied to describe heterogeneous flow phenomena through porous media. Under certain conditions,water and chemical movement in unsaturated soil is not just a simple one dimensional movement,instead often a heterogeneous flow situation,due to soil structures or wetting front instability. Preferential flow consists of macropore flow,funnel' flow,and finger flow. This paper reviews and summarizes studies on three types of preferential flow phenomena in theory,experiment and modeling.