By using the related remote sensing data, statistical data and the four main carbon sources of fertilizer, agro-film, tillage and agro-machinery in 2010, a calculation of the carbon sources and sinks of agro-ecosystem in Guanzhong area was made in reference to the improved CASA (Carnegie-Ames-Stanford Biosphere) model, taking county (district or city) as a unit. The findings are as follows: (1) The total carbon absorption of the Guanzhong agro-ecosystem was about 6.44×10⁶ tons, with the high values of carbon absorption in June, July and August and the low values in December, January, February and March. The counties whose value of carbon absorption was more than 2.0×10⁵ tons were distributed in the north of Baoji City, west of Xianyang City, and middle and southwest of Weinan City. (2) The total amount of carbon emission of the Guanzhong agro-ecosystem was about 1.46×10⁶ tons. Fertilizer was the main carbon source, accounting for 89%. The regions whose value of carbon emission was more than 60 000 tons were distributed in the middle of Weinan City and mid-south of Xianyang City. (3) The total carbon sink of the Guanzhong agro-ecosystem was about 5 033 500 tons. The value of carbon sink more than 200 000 tons was centered in the northwest of Guanzhong area.