Abstract: Moderate-scale operation of agricultural land is a key path to advancing agricultural modernization and safeguarding national food security. Clarifying the relationship between moderate-scale agricultural land operation and grain yield per unit area is a crucial issue for balancing high-quality agricultural development and food security. Based on provincial-level data from 19 major maize-producing provinces covering the period from 2009 to 2023, this study employed a fixed-effects model with Driscoll-Kraay robust standard errors to examine the impact of large-scale farmland management on maize yield and empirically tested its moderating effects. The findings were as follows: (1) There was a positive U-shaped nonlinear relationship between large-scale farmland management and maize yield, with an inflection point occurring at a large-scale farmland management level of 27.15%; this conclusion remained valid following robustness checks. (2) Moderating effect analysis showed that an increase in hired labor for maize production significantly strengthened the inhibitory effect of large-scale farmland management on maize yield, while improvements in maize mechanization rate and agricultural socialized services did not exhibit statistically significant moderating effects on the scale-yield relationship. Therefore, to coordinate large-scale farmland management with grain security, it is necessary to move away from a scale-oriented approach and establish a dynamic, tiered support system, strengthen the foundational support of mechanization and socialized services, and address the cost challenges of field management through specialized services and intelligent equipment.