Enhancing agricultural carbon emission efficiency (ACEE) is a pivotal pathway for advancing environmentally sustainable transformation in agriculture and achieving the ‘dual carbon’ targets. However, empirical evidence on whether and how new-quality productive forces in agriculture contribute to improvements in ACEE remains limited. Using a super-efficiency slack-based measure (SBM) model, this study estimates the performance of carbon emissions from agricultural activities for 30 Chinese provinces from 2011 to 2022. Based on provincial panel data, fixed-effects, mediation, and threshold-effect models are combined within a panel data framework to investigate the impact of agricultural new-quality productive forces (ANQPF) on ACEE and its underlying mechanisms. The results indicate that: (1) ANQPF exerts a significant positive effect on ACEE. (2) Land transfer and the level of agricultural socialized services serve as important transmission channels through which ANQPF improves ACEE. (3) The relationship between ANQPF and ACEE exhibits a pronounced threshold effect. Below the threshold, the positive impact is significantly strengthened; however, as population density increases, the marginal effect of ANQPF on ACEE gradually declines. (4) Heterogeneity analysis indicates that the enhancing effect of ANQPF on ACEE is more pronounced in non-resource-based provinces and major grain-producing regions. In light of these findings, the results suggest that ANQPF should be positioned as a core policy lever. Simultaneously, land transfer should be optimized, the development of agricultural socialized services should be strengthened, and region-specific policies should be formulated to achieve synergistic outcomes in agricultural carbon reduction, efficiency improvement, and green growth.