Aims <p>The fragile soil structure of coal mine dumps in arid and semi-arid regions presents a major obstacle to ecological restoration. Phytoremediation strategies enhancing soil porosity are critical, yet Arbuscular Mycorrhizal Fungi (AMF) inoculation efficacy in compacted soils combined with mixed planting remains unclear.</p> Methods <p>This study employed a two-factor experiment and 3D CT scanning to assess AMF inoculation and mixed planting effects on <i>Amorpha fruticosa</i> root morphology, soil pore structure, and infiltration at a northern China open-pit dump.</p> Results <p>Our results demonstrated that both AMF inoculation and mixed planting significantly improved soil porosity and root development. Notably, the combined treatment of AMF inoculation and mixed planting (A-M) yielded the most uniform distribution of connected pores within the soil cores and exhibited the highest model complexity in correlation analyses. Furthermore, A-M also maximized fractal dimension and permeability while reducing tortuosity and improving connectivity, attaining peak permeability. With respect to root morphology, both AMF and mixed planting led to substantial increases in root morphological characteristics and root density characteristics. Partial least squares path analysis revealed that the observed improvements in soil pore structure and infiltration characteristics were primarily driven by root morphological modifications induced by AMF and mixed planting treatments.</p> Conclusions <p>The synergistic application of AMF inoculation and mixed planting effectively optimized soil pore architecture and enhanced infiltration dynamics at open-pit dump sites, primarily through their stimulatory effects on plant root development. These findings provided a strong scientific foundation and practical guidance for advancing ecological restoration efforts in arid mining regions.</p>