Abstract: Guangxi is a major agricultural region in China, and the agricultural system is not only an important source of carbon emissions that cause global climate change, but also a significant pathway for carbon sequestration. To achieve the “dual carbon” targets in agriculture and high-quality development of the rural economy in Guangxi, this study comprehensively estimates the amount of agricultural carbon budget in Guangxi from 1978 to 2021. It also identified the key factors influencing agricultural carbon budget. Agricultural carbon budget, including carbon emissions, carbon sequestration, and net carbon sinks, was estimated and analyzed using total agricultural material inputs, paddy cultivated area, livestock and poultry farming, amount of crop residue burned, crop yield, and aquaculture production from Guangxi statistical database using the emission factors approach and the carbon sequestration parameter method. Based on this, the main factors influencing agricultural carbon budgets were identified using the revised Stochastic Impacts by Regression on Population, Affluence and Technology (STIRPAT) model. The results revealed that the value of carbon emissions, carbon sequestration and net carbon sink increased from 1166.61×10⁴ t, 872.81×10⁴ t and –293.79×10⁴ t to 1457.17×10⁴ t, 3271.57×10⁴ t and 1862.14×10⁴ t, with an average annual increase of 0.55%, 3.45% and 18.92%, respectively, from 1978 to 2021. In 1990, carbon emissions and sequestration reached a balance, then the net carbon sink from agricultural system showed a trend of first increasing and then stabilizing. From 1979 to 2021, carbon emissions from agricultural materials input showed an increasing trend, and it contributed to 36.44% of total carbon emissions. Carbon emissions from paddy field, livestock and poultry farming, and crop reside burning were 26.41%, 21.93% and 15.22% in 2021, respectively. Specifically, fertilizer application, medium rice cultivation, cattle breeding, and rice straw burning were the major contributors to carbon emissions. Carbon sequestration by crops has been the dominant source of carbon sequestration over the past several decades. Of these, sugarcane has increased and become the major source of carbon sequestration (57.35% in 2021), while rice carbon sequestration has declined from 75.57% in 1978 to 28.62% in 2021. Aquaculture accounts for about 10% of total carbon sequestration, with oysters accounting for 99% of aquaculture’s carbon sequestration. The STIRPAT model demonstrated that the agricultural carbon budget in Guangxi was affected by many factors. Carbon emissions were correlated with rice production and fertilizer application, and every 1% increase in the two factors led to 0.417% and 0.035% increases in carbon emissions, respectively. Carbon sequestration and net carbon sink were driven by the total agricultural population, level of agricultural economic development, fertilizer application, and crop yield. The total agricultural population and rice sown area had negative impacts on carbon sequestration and net carbon sink, while crop yield was the most influential factor. An increase of 1% in crop yield led to increase of 0.17%−0.39% in carbon sequestration. The results of this study showed that carbon emissions can be reduced and carbon sequestration can be increased through precision fertilization, intensive farming, and increased crop yields. The present results provide scientific data for policy formulation and agricultural carbon emission predictions.