Abstract: As a new goal and requirement for China’s agricultural development, the development of new quality productive force in agriculture has profound implications for rice yield, which is intrinsically linked to national food security. Although the existing research primarily explores the relationship between the development of new quality productive force in agriculture and grain production from a theoretical standpoint, this study systematically investigated the influence of new quality productive force in agriculture on total rice yield and the underlying mechanisms from both theoretical and empirical perspectives. It also considered the heterogeneous effects of new quality productive force in agriculture across different rice production scales and geographical regions. Based on provincial panel data from 2012 to 2023, a comprehensive evaluation index system for new quality productive force in agriculture was established in three key dimensions: agricultural laborers, subjects of labor, and labor means. This study employed the fixed effects, mediating effects, threshold, and spatial econometric models to rigorously test the proposed relationships. Our empirical findings provided several critical insights. First, new quality productive force in agriculture had a significantly negative impact on total rice yield. This result remained robust after accounting for potential endogeneity and conducting a series of robustness tests, including extreme value winsorization, an alternative dimensionality reduction method for indices of new quality productive force in agriculture, and the exclusion of selected subsamples. Second, the mechanism analysis showed that new quality productive force in agriculture had an adverse effect on the rice cultivation area, although it increased the yield per unit area. The magnitude of this area-reducing effect substantially outweighed the productivity gain per unit, leading to an overall decrease in the total rice yield. Third, the threshold regression results indicated that the relationships between new quality productive force in agriculture and both total rice yield and yield per unit were nonlinear and contingent on the scale of the rice-planting area. Specifically, when the rice planting area exceeded the threshold values of 3.3810 and 2.8214 (in standardized units), the effects of new quality productive force in agriculture on total rice yield and per unit yield shifted from negative to positive, respectively. In addition, the regional heterogeneity analysis highlighted distinct spatial patterns. New quality productive force in agriculture significantly reduced the total rice yield in central China, whereas it significantly increased the total rice yield in the western region. Similarly, it significantly boosted the total rice yield in major rice-producing zones, whereas it had the opposite effect in non-major rice-producing zones. Finally, the negative influence of new quality productive force in agriculture on total rice yield exhibited spatial spillover effects, which indicated that it not only reduced the total rice yield in the local region but also negatively affected the yield in neighboring areas. In light of these findings, new quality productive force in agriculture may conflict with the goal of total yield stabilization in key staple crops such as rice. Therefore, to harmonize the advancements of new quality productive force in agriculture with total rice yield assurance, it is imperative to implement integrated measures that fully safeguard rice cultivation areas, optimize the regional development layout, and improve the scale of rice production.