[Objective] To elucidate the mitigation mechanisms of arbuscular mycorrhizal fungi（AMF）inoculation on soil nutrient and moisture supply deficiencies，thereby supporting the sustainable restoration of fragile karst ecosystems. [Methods] Based on an in-situ inoculation experiment in plantation plots of a typical karst rocky desertification area in Shaoyang County，Hunan Province，fine roots at 0-15 cm and 15-30 cm soil depths and soil samples at 0-15 cm，15-30 cm，and 30-50 cm soil depth were collected from upper，middle，and lower slopes. AMF infestation status，community composition，and soil physicochemical properties were measured to clarify the effects of key microbial additions on soil nutrients and moisture. [Results] The results showed that inoculation increased the infestation rate and intensity of root AMF. At the genus level，Paraglomus，Glomus， and Ambispora were the dominant genera in the AMF community，and their relative abundances changed significantly after inoculation，with differences across slope positions and soil layers. After inoculation，the Simpson's diversity index increased in the 0-15 cm layer at all slope positions，in the 15-30 cm layer at the mid-slope position，and in the 30-50 cm layer at the mid-lower slope position，but the differences were not significant. The Chao1 richness index increased across all layers，with a significant difference only at the upper slope position in the 0-15 cm layer. The Pielou's evenness index increased in the 0-15 cm layer at the mid-upper slope position，in the 15-30 cm layer at the mid-slope position，and in the 30-50 cm layer at all slope positions，but the differences were not significant. The mass fraction of alkali-hydrolyzable nitrogen（AN） decreased in all layers，the mass fraction of available phosphorus（AP）decreased only in the 15-30 cm layer， and the soil organic carbon mass fraction decreased in the 0-15 cm and 15-30 cm layers，but the differences were not significant. Soil volumetric water content（VWC）increased significantly in all soil layers，capillary porosity（CP）increased in the 0-15 cm and 30-50 cm layers，and pH and exchangeable Ca²⁺ decreased in all layers，but the differences were not significant. The AN：AP ratio showed a decreasing trend in the 0-15 cm and 15-30 cm layers，indicating that AMF inoculation could partially alleviate phosphorus limitation in the soil. Correlation and redundancy analysis indicated that changes in microbial community composition after inoculation directly or indirectly affected soil physicochemical traits including nutrients and moisture. [Conclusion] The results clarify the response characteristics of soil properties to AMF inoculation in karst rocky desertification plantation forests and identify nutrient and moisture changes and their driving factors，which helps overcome the bottleneck of delayed soil ecological function restoration and improves the service functions of fragile ecosystems.