The protection of cultivated land serves as a crucial foundation for ensuring its ecological security, improving the performance of ecological welfare derived from cultivated land, and enhancing the well-being of farmers. Based on panel data from 49 study units across four provinces and municipalities-Yunnan, Guizhou, Sichuan, and Chongqing in Southwest China from 2010 to 2022, this study employed analytical methods including the super-efficiency SBM model with undesirable outputs, spatial lag model, and threshold regression model. It evaluated the ecological security level of cultivated land and the performance level of its ecological welfare in the study area, along with the impact of cultivated land ecological security on ecological welfare performance and the critical thresholds of key influencing factors. The results showed that: 1) From 2010 to 2022, both the ecological security level of cultivated land and its ecological welfare performance exhibited an overall upward trend across the study area. The spatial pattern of both was generally characterized as "high in the north and low in the south." High-value areas for both indicators were concentrated in the Sichuan Basin, while low-value areas were primarily located in southern Yunnan. Significant spatial heterogeneity was observed, although it gradually weakened, indicating a trend toward balanced development. 2) Cultivated land ecological security exerted a significant positive effect on its ecological welfare performance. It influenced ecological welfare performance through natural value spillover and experiential technology spillover, demonstrating a notable positive spatial spillover effect to adjacent areas. Improvements in the ecological security of cultivated land in one region not only enhanced its own ecological welfare performance but also had a positive effect on that of neighboring regions. 3) The impact of cultivated land ecological security on its ecological welfare performance exhibited distinct single-threshold effects for both farmland operation scale and crop planting structure. The critical threshold values were 0.516 hm² per person and 48.901%, respectively. When these thresholds were exceeded, the positive non-linear influence strengthened significantly. At the same time, the thresholds for farmland operation scale and crop planting structure exhibited significant regional differences.Future regional cropland protection policies should emphasize locally adapted strategies to promote appropriately scaled farmland management, rationally adjust crop planting structures, and optimize the proportion and varieties of economic crops. Efforts should also be strengthened to enhance inter-regional cooperation and exchange, further safeguard cropland ecological security, and foster the continuous improvement of farmland ecological welfare performance.