Under the background of continuously shrinking cultivated land resources, increasing grain yield per unit area is a core pathway to ensuring national food security. Agricultural mechanization, serving as a crucial support for integrating high-standard farmland with optimized agronomic practices, plays a vital role in enhancing grain production capacity. Focusing on Jiangsu Province, this study systematically analyzed the contribution characteristics of mechanization to yield growth based on the dynamic changes in grain yield over the past five years. The results indicated that since the onset of the 14th Five-Year Plan, the contribution rate of yield increase to total grain production has continued to decline, highlighting an urgent need to unlock potential for further yield improvement. Field surveys reveal that key constraints include a weak foundation for farmland mechanization suitability, insufficient mechanization in critical production links, low integration of machinery and agronomy, inefficient social service systems, and a shortage of professional technical personnel. By examining typical practices in Northern, Central, and Southern Jiangsu, this paper summarizes development experiences centered on government guidance, entity-driven initiatives, machinery-agronomy adaptation, and smart upgrading. Consequently, an optimized pathway is proposed, emphasizing mechanization suitability transformation, the construction of a full-process mechanization system, collaborative technology integration demonstrations, diversified social service improvement, and modern agricultural talent cultivation. These findings provide references for promoting high-quality agricultural mechanization development and sustaining comprehensive grain production capacity in Jiangsu Province.