【Objective】Sichuan, Chongqing, Guizhou, and Yunnan Province in Southwest China constitute the core distribution area of yellow soil drylands in China. This region is characterized by a high proportion of medium- and low-yield croplands, facing significant challenges on agricultural productivity enhancement. Consequently, precisely identification of limiting factors and quantification of yield potential is critical to ensure national food security. 【Method】This study constructed a comprehensive cultivated land quality evaluation framework based on multi-source geospatial datasets, including the High-resolution National Soil Information Grid of China (90 m resolution) from 2010 to 2018. By employing the optimal parameters-based geographical detector model and the NDVI (Normalized Difference Vegetation Index)-based grain yield estimation approach, the spatial distribution, constraining factors, and productivity enhancement potential of medium- and low-yield croplands on yellow soil drylands in Southwestern China were systematically analyzed. 【Result】The results showed that: (1) The regional drylands exhibited distinct spatial fragmentation. Medium- and low-yield croplands covered 3.4442 million hectares, accounting for 89.71% of the total cropland area, with a spatial distribution ranking: Guizhou Province > Sichuan Province > Yunnan Province > Chongqing Municipality. (2) Field management (e.g., irrigation capacity, q = 0.60) and site natural conditions (e.g., terrain position, q = 0.26) were the key constraining factors limiting cultivated quality improvement. Among soil physicochemical properties, synergistic constraints involving pH, bulk density, and soil organic carbon (SOC) content were identified as statistically significant limiting mechanisms. (3) Grain yield in medium- and low-yield croplands showed a heterogeneous spatial distribution pattern, charactering as "high-value patches embedded within contiguous low-value zones". It increased gradually at lower grades, followed by accelerated increases upon reaching higher quality thresholds. (4) Scenario-based simulations indicated that improving the cultivated land quality grade of medium- and low-yield croplands by 0.5, 1.0, 1.5, and 2.0 grades would increase regional grain yield by 2.94%, 5.24%, 8.04%, and 11.47%, respectively, equivalent to conserving 61 800～241 000 hectares of cropland area. (5) Feasible pathways and implementation challenges associated with quality improvement and productivity enhancement for medium- and low-yield croplands on yellow soil drylands in Southwest China were preliminarily analyzed. 【Conclusion】This study systematically reveals the obstacle mechanisms and improvement potential of medium- and low-yield yellow soil drylands in Southwest China, thus can provide a scientific basis for implementing the governance strategy of "obstacle diagnosis-quality improvement-productivity enhancement" in this region.