Crop farming, along with ensuring national food security, is also an important source of greenhouse gas (GHG) emissions in the agricultural sector, and therefore acts as a crucial role in global warming. As the world"s leading agricultural producer, China feeds 20% of the global population with only 7% of global croplands through constantly improvement of agricultural practice including the increased input of fertilizers and pesticides over the past decades. With the implementation of the Sustainable Development Goals of the United Nations and China"s carbon neutral strategy, accurate estimation of GHG emissions from crop farming has a significant position in the path of realizing the carbon peaking and carbon neutrality goals in China"s agriculture. However, a comprehensive, long-term, and spatially-precise profile of GHG emissions from crop farming is still lacking in China. In order to accurately understand changes of historical emissions and their implications for future mitigation, this study quantitatively analyzed the dynamic changes and spatial differentiation patterns of GHG emissions in China"s crop farming from 1978 to 2020 at the national and provincial scales, respectively, based on multi-source statistical data. The results showed that the total GHG emissions from China"s crop farming had a significant increasing trend from 1978 to 2020 (p < 0.01). However, there were two significant decreases from 1997 to 2003 and from 2012 to 2020. Furthermore, the reasons for these decreases were not the same, so that the GHG emission intensity (i.e., GHG emissions per unit of grain production) showed opposite changes in these two periods. Particularly in the period from 2012 to 2020, there was a decrease in GHG emissions and an increase in grain production, which resulted in a decrease in GHG emission intensity of nearly 20%. This finding showed a synergistic realization of the goals of increased grain production and GHG emission reduction. From 1978 to 2020, GHG emissions from crop farming at the provincial scale showed a spatial difference of higher in the south and east as well as lower in the north and west, and the overall pattern corresponds well to the distribution of the mean value of grain production. However, grain production increased from 2012 to 2020 in most regions of China, whereas the GHG emission intensity decreased in these regions to different degrees, mainly due to the reduction of chemical fertilizer and pesticide use. Specifically, the application of nitrogen fertilizers and pesticides declined to different degrees from 2012 to 2020 in Northeast China, North China, Jianghuai, and Sichuan-Chongqing regions, which did not affect the increase of grain production, but also contributed to the reduction of GHG emissions. The results of this study showed that the implementation of ecological civilization construction policies has made a positive contribution to the cultivation industry to achieve the goal of carbon peaking and carbon neutrality under the premise of ensuring China"s food security.