The extreme weather caused by the global warming effect has triggered huge losses to agricultural production. A hot issue for governments and scholars is how to effectively reduce carbon emission intensity in agriculture. The agricultural farming practices that are high pollution and high energy cosuming have exacerbated the vulnerability of regional agroecosystems. The sustainable development of agriculture is faced with the two dilemmas of a low utilization rate of green resources and the serious pollution of farmland. Further, environmental and ecological carrying capacities have reached their limits, seriously hindering the high-quality development of low-carbon agriculture in China. Thus, based on the panel data of 282 cities, the Spatial Dubin Model (SDM) is employed to examine the impact of agricultural mechanization on carbon emission intensity in agriculture. It is found that from 1999 to 2019 carbon emission intensity in agriculture showed an overall downward trend; as of 2019, the agricultural field had completed the target of carbon emission reduction, one year ahead of schedule. From a local perspective, approximately 14.89% of agricultural industries in prefecture-level city have still not achieved carbon emission reduction targets, and agricultural carbon emission reduction tasks were better completed in major grain-producing areas than in nonmajor grain-producing areas. Agricultural mechanization has significantly reduced carbon emission intensity in local agriculture production. The impact of agricultural mechanization on carbon emission intensity in agriculture has not only a significant negative spatial spillover effect but also a significant effect on spatial carbon emission reduction. Compared with non-major grain-producing areas, agricultural mechanization plays a greater role in reducing spatial carbon emissions in major grain-producing areas. Further studies find that agricultural mechanization is conducive to overcome difficulties, such as instability of property rights and land fragmentation, and to achieve large-scale agricultural production, thereby reducing agricultural carbon emissions in nearby regions. However, the transfer of rural labor, adjustments to the structure of agricultural cultivation, and the centralized use of rural land restrict the development of the crossregional service market for agricultural machinery, which in turn weaken its contribution to spatial carbon emission reduction. At the end of this paper, it is suggested that Chinese governments at all levels should introduce subsidy policies for the cross-regional operation of agricultural machinery to solve the problem of their service market failure. Efforts should be made to stimulate the market to develop more energy-efficient and environmentally friendly agricultural machinery products while strictly controlling changes in the use of arable land in non-grain-producing areas, which aims to serve further agricultural mechanization and boost the high-quality development of low-carbon agriculture.