[Objective] The carbon source and sink of farmland ecosystem were illustrated to provide a reference for the crop types and cropping patterns of oasis farmland. [Methods] Based on the collected data of main crop production, arable land, crop cultivated area and agricultural inputs data in Zhangye City during 2001-2010, the carbon absorption, carbon emissions and carbon sinks of farmland ecosystem of each county were estimated using models of agricultural carbon sequestration, and carbon emission, and the temporal and spatial distribution of these indices were analyzed. [Results] There were obvious temporal and spatial differences in carbon absorption, carbon emission and carbon sink. The carbon absorption intensity was found only positively relevant to crop yield per unit area. The per unit change of cotton among the economic crops, and the soybean among grain crops had the maximum contributions to carbon absorption. The total carbon emission was a function of the chemical fertilizers, crop cultivated area, the total power of agricultural machinery and irrigation area. The unit volume change of chemical fertilizers had the maximum contribution rate to carbon emissions, and the carbon emissions showed an increasing trend. The contribution of irrigated area followed and it had a decreasing trend year by year. Agricultural machinery had the minimal proportional contribution, with a less than 5% of total carbon emissions. [Conclusion] In recent 10 years, the total carbon absorption showed a significant increasing trend, while the carbon emissions showed a decreasing trend, all of which indicated that the farmland ecosystem of Zhangye City had a strong capacity of carbon sink.