The inversion of the lower interface of magnetic media on the basis of magnetic anomaly is a nonlinear problem. which it generally difficult to solve directly. Through lineatrzation of nonlinear problems. the authors established the linear discrete magnetic modeland, using regular algorithm of linear programing, designed a scheme for iterative solution,which does not require sverage depth of known interface relief, and only needs the auppositionthat the interface is continuous and that magnetism changes laterally. As the algorithm isready to exert physical constraint upon the solution. the method is characterized by rapidconvergence and high precision.