Abstract: Based on the development background of adhering to the big food concept to coordinate diverse food resources, enhance the efficient utilization of agricultural land, and improve the capacity for food supply assurance, this study used panel data from 11 provincial-level administrative regions in western China from 2013 to 2023. The Super-SBM model was adopted to measure agricultural land use efficiency, combined with ArcGIS spatial analysis to reveal its spatiotemporal evolutionary characteristics, and the geographically and temporally weighted regression (GTWR) model to identify the spatiotemporal heterogeneity of influencing factors and their driving pathways. The results indicated that: (1) The agricultural land use efficiency in western China showed a phased pattern of “low-efficiency slow increase in the early stage, followed by a leap to effective levels in the later stage”, with comprehensive technical efficiency reaching a relatively effective level (mean ≥ 1) after 2020, though significant regional differences persisted, with the northwest region outperforming the southwest. (2) The relatively higher agricultural land use efficiency in the northwest region was primarily attributed to the continuous improvement in pure technical efficiency. (3) The influencing factors exhibited spatiotemporal heterogeneity in both the degree and direction of their effects on agricultural land use efficiency. Accordingly, it is necessary to implement region-specific quality and efficiency improvement measures, optimize the diversified food supply structure, and refine the factor support system, so as to enhance agricultural land resource utilization efficiency and diversified food supply capacity in western China.