Abstract: Owing complex boundary conditions of river channels and the requirements of calulation accuracy, how to conduct quickly effective dissection of grids is very important for the FEM Calculation.On the basis of advancing-front methed, a new method suitable for atuo-dissection of river channels in 2-D region was proposed and a river-channel mesh auto-dissection system established.This method is simple, reliable and of strong suitability.It can implement the functions of mesh auto-generation, geography auto-dissection and figure auto-drawing, and , thus, it has solved a difficult problem how to quickly handle enormous working-load before the riverchannel FEM calculation