In the old finite difference method for groundwater flow model, the hydrogeology parameters are same in a triangle unit, and parameter areas are divided according to the triangle units which have same parameters. This method can be used to solve the most simulation and forecast problems of groundwater flow models, but there are some limits for heterogeneous and anisotropy problems. The paper states a new parameter area dividing method base on the area which be controlled by the sides of the triangle unit, and sets up the finite difference equation under the new parameter area dividing method and nonsame parameter in a triangle unit, then gives a applying example. The method is more accurate for describing or simulating heterogeneous and anisotropy problems, also compatible with the old finite method.