The research region is divided into many rectangles with fixed width, and densities and thicknesses of the rectangle units are taken as model parameters. On this base, the objective function of inversion of gravity anomaly is formed, and the partial derivative tensors for the model parameters are also calculated. Then the Ridge Regress Procedure is employed to inverse gravity anomaly in order to obtain the densities and their interfaces.The method is used in inversion test for two theoretical models.