Abstract: Water resources are scarce in western China, where microbial reclamation technology is increasingly applied to mine dumps and preliminary ecological benefits are achieved. Soil pores are a key factor affecting soil water transport and retention, whereas conventional measurement methods are limited in quantitatively characterizing soil pore features. Based on three-dimensional reconstruction of soil pores and the multifractal method, the development characteristics of soil pores in reconstructed soil layers of a dump under inoculation conditions are investigated using a laboratory soil-column simulation experiment. The soil column consists of three layers: a topsoil layer, a water-retaining layer, and a water-barrier layer. Two treatments, inoculation with arbuscular mycorrhizal fungi (AMF) and a control (CK), are established, and Amorpha fruticosa is used as the test plant. The results show that soil pores exhibit multifractal characteristics, and the results of multifractal characterization are consistent with the variation in soil porosity, indicating that the multifractal method can be used for the quantitative characterization of soil pores in reconstructed soil layers. Across the entire soil profile, the multifractal parameters D(0), D(1), ΔD, and Δα are all higher under the inoculation treatment than under the control, indicating that soil pore conditions are improved by inoculation and that pore distribution becomes more complex, more heterogeneous, and less uniform. In the topsoil layer, mean pore volume, mean pore diameter, mean throat diameter, and mean throat length are increased by 137%, 36%, 65%, and 23%, respectively, under the inoculation treatment; in the water-retaining layer, the corresponding increases are 84%, 14%, 54%, and 13%, respectively. These results indicate that the development of connected pores in different soil layers is promoted by inoculation. The multifractal parameters D(1) and ΔD, together with mean throat length, show relatively high explanatory contributions to Amorpha fruticosa biomass and are identified as key factors affecting its growth. Therefore, the multifractal method combined with the soil pore network model enables refined quantification of pore-structure development and can be used to evaluate soil pore development in reconstructed soil layers of open-pit coal mine dumps in western China, thereby providing technical support for the assessment of soil structure in mine dumps.