In the context of low-carbon transformation in agriculture, accurately understanding the spatio-temporal evolution of carbon effects and the characteristics of carbon equity in grain cultivation is crucial for achieving regional ecological justice. Based on provincial panel data from 2000 to 2021, the carbon emission factor method was used to measure and analyze the spatial and temporal characteristics of carbon effects in food cultivation across 30 provinces, municipalities, and regions in China. At the same time, the kernel density estimation method was applied to explore the dynamic evolution of carbon effects. Furthermore, this paper employed the Dagum Gini coefficient method to characterize and deconstruct the equity of net carbon sinks in nationwide food cultivation based on the net carbon sink intensity index. The following key findings are revealed: (1) From the perspective of spatial and temporal characteristics, the total net carbon sink of the grain farming industry fluctuated and rose during the investigation period. Notably, it exhibited a spatial pattern of "low in the west and high in the east, low in the south and high in the north", accompanied by the obvious "Matthew effect". Additionally, straw burning and corn gradually emerged as the primary carbon source and carbon sink. (2) From the perspective of the evolution trend, the spatial non-equilibrium of the carbon effect of the national grain cultivation industry had been expanding. Among them, the non-equilibrium in carbon effects of main rice-producing areas was decreasing, while wheat and maize exhibited a continuous increase in non-equilibrium. (3) From the perspective of carbon emission equity, inter-regional difference had become the primary factor affecting equity, with the contribution rate of 35.250% in 2021. In addition, Gini coefficient was characterized by "rapid growth-fluctuation shock-slow decrease", and the carbon emission of the national grain farming industry remained within a relatively equitable range during the examination period, with the overall equity improving. Among the main production areas of the three major staple grains, the main maize producing area demonstrated the highest degree of fairness, while the main rice producing area showed the least fairness. Finally, suggestions such as adopting differentiated carbon sequestration and emission reduction strategies for the grain farming industry, building a cross-regional collaboration mechanism for low-carbon development of the grain farming industry, perfecting the carbon emission responsibility-sharing mechanism, and exploring grain carbon sink trading pilots were proposed with a view to boosting China's grain farming industry to realize low-carbon transformation.