The corrosion fault diagnosis of grounding grid requires multiple incentives and repeated measurement to get locations of the fault branches. In order to solve this problem, this paper established diagnostic equations of grounding grid fault based on the conservation between input power and consumed power, and solved the nonlinear programming problem, which indicated the approximate locations of the fault branches in the grounding grid by measuring only one time. Experiment results proved the feasibility and practicability of the diagnosis method described in this paper and indicated that it had practical value for diagnosing the locations of fault branches in small-scale grounding grid. (Wei Zhang et al. 2018, Huizhong Xu et al. 2009).