Even though solid backfill mining can address some environmental issues of coal mining (like surface subsidence and gangue storage), on the other hand the long exposure of gangue to rain or other surficial water will also result in the leaching of heavy metal ions, which in turn will pose the threat of potential pollution to groundwater. In response to resolving the above-mentioned problem, this paper simulated the concentration distribution and migration principle of Cu²⁺ in various soils by applying COMSOL Multiphysics software, and the results show that the diffusion distance of Cu²⁺ in different soils are ranked as clay, silty clay, loess, and sandy soil. In addition, the concentration will decrease with the increase of depth and the Darcy velocity contours of Cu²⁺ distribute radially and symmetrically in the transverse direction. The velocity gradient of Darcy velocity in different soils is clay soil > Silty clay soil > loess > sandy soil.