Abstract: Clarifying the plant water use strategy and its response characteristics to soil moisture under long-term mycorrhizal reclamation in coal mining subsidence areas in semi-arid regions is an important basis for the sustainable development of mining ecological reclamation. This study focuses on the long-term mycorrhizal reclamation of the Daliuta coal mining subsidence area in northern Shaanxi. Isotope tracing, direct correlation method, Bayesian mixed model (Mixing Model with Stable Isotope Analysis in R, MixSiAR), and other methods were used to analyze soil moisture, root distribution, water use ratio, and efficiency indicators of purple locust sample plots after mycorrhizal reclamation (Arbuscular Mycorrhizal Fungi, AM) and vegetation reclamation for 10, 9, and 8 a. The results showed that there was no significant difference in water content in the shallow soil layer under long-term reclamation, while mycorrhizal reclamation had a significant water retention effect in the deep soil layer (below 1.5m) , with an increase of 16.5%, 33.6%, and 51.0% after 10, 9, and 8 a of reclamation, respectively. Based on the rate of soil moisture change in the longitudinal profile, all reclamation treatments showed a deficit in soil moisture content within a depth of 1 meter. Compared with the CK treatment, the average rate of soil moisture change in vegetation reclamation was −33.9%, while the mycorrhizal reclamation treatment increased by an average of 39.7%. The coincidence degree of hydrogen and oxygen isotopes between the water in the xylem of sophora japonica and soil water is greater than 95%, indicating that the degree of fractionation of water in the xylem of sophora japonica is relatively small, while the isotopic composition of deep soil water tends to be stable. Compared with vegetation reclamation, the δD and δ¹⁸O of water in mycorrhizal reclamation showed similar trends, and the intersection of xylem water and soil water in all treatments of sophora japonica generally shifted downwards, indicating that the water use layer of sophora japonica was deepened after inoculation treatment. The absolute utilization of soil water by all treatments of sophora japonica showed that surface soil water was the main source, and the cumulative soil profile water use efficiency showed that mycorrhizal reclamation was mainly based on shallow and deep soil water, with an average increase of 11.2% and 9.1% in the utilization ratio and efficiency of deep soil water. In summary, long-term mycorrhizal reclamation has optimized the water use strategy of reclaimed vegetation, which is beneficial for water retention in coal mining subsidence areas and promotes sustainable positive ecological succession in mining areas.