<p>Soil leaching is an effective soil remediation technology for heavy metal contamination, yet the mechanistic disparities between combined and stepwise leaching remain underexplored. In this study, a new adsorbent material—CSP@NA-2.0 was synthesized from chitosan and hydroxyapatite for combined leaching and two-step leaching of Cu-contaminated soils. The effects of compounding combinations, compounding ratios, rinsing liquid–solid ratios, rinsing solution pH, rinsing time, on the remediation of combined leaching and the leaching sequence on the remediation of two-step rinsing were investigated, and analyzed the mechanism of the two methods and the effect on soil physicochemical properties. Results showed that the CSP@NA-2.0+ citric acid combination exhibited the best performance: under optimal conditions, combined leaching removed 81.9% of unstable Cu, outperforming two-step leaching (average 76.2%). Adsorption kinetics aligned with Elovich and two-constant models, indicating Cu desorption was governed by heterogeneous diffusion. Both methods minimally altered soil pH and increased organic matter content while decreasing the effect on the amount of active nutrients (P, N, K). Therefore, the efficiency of combined leaching was better than two-step leaching in this experiment, which was attributed to the synergistic effect between CSP@NA-2.0 and citric acid: CSP@NA-2.0 provided abundant carboxyl, hydroxyl and amino binding sites, while citric acid promoted the solubilization and complexation of Cu through its acidic environment and multicarboxylic structure. This study highlights the potential of CSP@NA-2.0 as a high-performance and environmentally friendly leaching material, providing a scientific basis for the selection of the optimal soil remediation strategy for heavy metal pollution.</p>