Addressing the insufficient research on the corrosion characteristics of large hydropower station grounding grids, this paper constructs a model of a large hydropower station grounding grid based on CDEGS software, systematically studying the impact of conductor corrosion and breakage on key parameters of the grounding grid’s operational state. By establishing models of the hydropower station’s soil and grounding grid, the influence of corrosion, local breakage, and zonal conductivity failure on key parameters such as grounding impedance, step voltage, touch voltage, and potential difference within the grid is revealed. Simulation results indicate that conductor corrosion significantly increases these parameters, with particularly drastic changes under extreme thinning conditions, highlighting clear safety risks. Additionally, while local breakage in corner areas has limited impact, zonal conductivity failure can cause sudden changes in local parameters. The research findings provide a basis for the quantitative assessment of grounding grid conditions and offer optimization suggestions for design redundancy, protective measures, and operational monitoring, holding significant engineering guidance value.