To investigate the influence of soil properties on the propagation of lightning electromagnetic fields (LEMFs) over mountainous terrain, a two-dimensional algorithmic model based on the finite-difference time-domain (FDTD) method was established. A porous soil conductivity model was incorporated to evaluate the lightning electromagnetic fields(LEMFs) at a nearby observation point under different mountain slopes, considering various soil types, water content and porosities. The results indicate that the horizontal electric field is more sensitive to changes in soil properties. Under high porosity conditions (25%), the peak horizontal electric field increases by approximately 67% when the soil water content decreases from 50% to 1%. Conversely, with low water content (1%), the peak horizontal electric field increases by about 54% when the soil porosity rises from 1% to 25%. Additionally, under varying mountain slopes, the horizontal electric field is more susceptible to soil water content in steep terrain, while the effect of soil porosity remains consistent regardless of the slope. These research findings quantify influence of different soil type on lightning electromagnetic fields, identify the geological conditions associated with high lightning-strike risk, and provide an important scientific basis for optimizing the siting of critical infrastructure and improving lightning disaster early warning in complex terrains.