Face on the problems of existed method of substation ground grid corrosion searching, like blindness, heavy workload, low working efficiency. Through the analysis of the ground grid fault diagnosis theory, using the theory of electric network and ideas of matrix, we can construct fault diagnosis equations. Introducing lowest energy principle and advanced optimization algorithm, substation ground grip corrosion fault point diagnosis problems have been effectively solved. Plus, we worked out relevant software of fault point diagnosis. At the same time, we have done some simulations, through the simulation examples verified this method is correctness and feasibility and practicality.