Abstract: Soil layering heterogeneity is a critical factor affecting the accuracy of impulse grounding impedance calculations for grounding grids. Traditional uniform soil models exhibit significant errors when computing the impulse characteristics of grounding grids and struggle to accurately reflect real-world soil conditions. By establishing a modified model that accounts for soil layering characteristics and employing a numerical calculation method combining the method of moments and the finite element method, this study analyzes the influence patterns of different soil resistivity ratios, layer thicknesses, and grounding conductor parameters on impulse grounding impedance. The research demonstrates that soil layering heterogeneity significantly affects the impulse dispersion characteristics of grounding grids. The modified model effectively improves calculation accuracy and provides theoretical support for the optimal design of grounding grids.