[Objective] To understand the basic evolutionary trend of carbon sources/sinks of farmland ecosystem of Jiangsu Provinc in recent years and identify the important sources of carbon emission in the process of agricultural development, in order to guide the development of low carbon agriculture.[Methods] The carbon estimation model was used to estimate the quantities of carbon emission, carbon uptake and carbon footprint, respectively. And the dynamic changes of the carbon footprint were analyzed.[Results] ① The total carbon emissions of farmland ecosystem tended to increase. The carbon emissions in 2016 (4.60×10⁶ t) were increased by 3.4% compared to 2001 (4.44×10⁶ t), and fertilizer was the main contributor to carbon emission. The intensity of the carbon emission showed a decline trend, and it was lower than 1 t/hm² at all stages. ② The carbon uptake showed an increasing trend. From 2001 to 2016, it increased by 3.57×10⁷ t, the annual compound growth rate was about 2.2%, and the carbon uptake per unit area showed an overall increase trend. The carbon uptake of horticultural crops was significantly higher than that of food crops and cash crops. ③ The carbon footprint of farmland ecosystems showed a declining trend, and there was a large ecological surplus.[Conclusion] ① The quantities of carbon absorption of farmland ecosystem was significantly higher than carbon emission from 2001 to 2016, which showed that the farmland ecosystem had good carbon sequestration capacity and could be used as the carbon sink. ② The impact of agricultural inputs on carbon emission was different, and the fertilizer was the most critical factor affecting agricultural carbon emissions.