Simulated experiments of grounding grid corrosion were conducted based on two 220 kV substation models. In initial diagnosis, the measurement nodal points were planned to great span, small piecemeal, and large piecemeal jointing fixed points. A comparative study of the three measurement plans was carried out. The results show that the large piecemeal with fixed points had the best performance and could be used as a practical method for diagnosing grounding grid corrosion.