To address the challenges in vegetation restoration caused by water scarcity during ecological rehabilitation in arid and semi-arid mining areas, field studies systematically investigating whether arbuscular mycorrhizal fungi (AMF) can mitigate these issues by regulating root architecture and plant water use strategies remain scarce. Therefore, based on a 10-year field control experiment from 2012 to 2022, this study focused on Hippophae rhamnoides, a typical pioneer species in the Daliuta Coal Mine area, to systematically evaluate the effects of AMF (Funneliformis mosseae BGC XJ01) inoculation on its root morphology, soil water acquisition, water use strategies, and water-use efficiency (WUE). Field observations were performed during the 2022 growing season (May and October) using an integrated approach combining root morphological characterization, stable isotope analysis (delta 2H, delta 18O, and delta 13C), and the MixSIAR Bayesian mixing model. The results demonstrated that AMF inoculation substantially altered the root system architecture of H. rhamnoides, leading to substantial increases in total root length density, root volume density, and root surface area density by 57.21%, 205.87%, and 103.83%, respectively, accompanied by a coordinated enhancement across fine, medium, and coarse root classes. Stable isotope evidence coupled with MixSIAR outputs further indicated that AMF inoculation induced a pronounced shift in plant water-use patterns toward deeper soil horizons (100-300 cm), increasing the contribution of deep soil water by 12.70% in May and 11.00% in October, thereby enhancing drought resilience during seasonal water scarcity. In addition, leaf delta 13C signatures revealed a significant improvement in long-term WUE following AMF inoculation, with the strongest response observed during the late growing season. From the perspective of an integrated "root-soil-water" feedback framework, these findings elucidated the mechanistic pathway through which AMF facilitated vegetation establishment and persistence in mining-disturbed landscapes, offering a robust microbial-based regulatory strategy and practical technical reference for ecological restoration in arid and semi-arid coal mining areas.