Reducing agricultural carbon emissions is of great  practical significance to accelerate the realization of Chinas “double carbon” goal. The effect and mechanism of agricultural land scale management on agricultural carbon emissions were investigated, by using panel fixed effect model and intermediary effect model, and the inter provincial panel data from 2000 to 2022, and meanwhile the regional heterogeneity was analyzed. The results show that a 1% increase in the scale of agricultural land operations would result in a 0.01% reduction in agricultural carbon emissions. The mechanism lies in the fact that the scale of farmland operations works through three mediating variables such as agrochemical input intensity, agricultural technological progress and cropping structure. In specific, for every 1% increase in the scale of agricultural land management, the intensity of agricultural chemical inputs will decrease by 0.06%, agricultural technological progress will increase by 0.69%, and the planting structure will show a “grain oriented” trend. These changes are conducive to agricultural carbon reduction. By region, the expansion of the scale of agricultural land management will significantly reduce agricultural carbon emissions in the eastern and northeastern regions, but will raise agricultural carbon emissions in the western region. Thus, to promote the lowcarbon development of agriculture in China, it is necessary to guide agricultural producers to appropriately expand the scale of agricultural land management, reduce fertilizer use and adopt lowcarbon production technologies.