Net primary productivity (NPP) and its response to global change is an important factor to consider in research in this field. A significant pool of carbon (C) is stored in agriculture soils. Crop biomass returned to the soil supports the maintenance of soil organic carbon (SOC). Studying the NPP, and its spatial variation aids SOC balance definition and help elucidating soil carbon dynamics in agroecosystems. In this study, we established a new data bank of dry coefficient (DC), harvest index (HI), and root to shoot ratio (R/S) for rice, wheat, corn grain, soybean, cotton, and oilseed crops based on field samples collected across China from 2011 to 2012. The data bank represents the most recent reference coefficients available in China. Using county-level crop yield information, reported as national agricultural statistics, combined with the DC, HI, and R/S for rice, wheat, corn grain, soybean, cotton, and oilseed crops, we estimated the amount of NPP produced in 2010, and analyzed its spatial distribution. It was estimated that 596 Tg C was produced in 2010 in China's cropland, mainly distributed in the Huanghuaihai region, the Middle-Lower reaches of Yangtze River and Northeast China. The mean county-level NPP density was 519 g C m^-2 a^-1, ranging from 9 to 2094 g C m^-2 a^-1. The NPP produced in China's cropland represents 8% of global crop biomass, suggesting that it makes a large contribution of the croplands, which add to the world's carbon pool. Greater county-level NPP density (g C m^-2 a^-1) (NPPD) primarily exists in the humid and semi-humid regions of eastern China, as well as in the regions of northwest China with more developed irrigation. Lower NPP density occurs in arid and semi-arid regions of northwest China. The Huanghuaihai region produced the largest NPP among 9 agricultural regions. While the area of sown land accounted for 98% of this difference, the density of NPP could only explain 31% of the variance among the 9 agricultural regions. The NPPD of Northeast China was the highest and that of the Qinghai-Tibet Plateau as the lowest. In order to assess the impact of climate and fertilizer on NPPD in all 9 agricultural regions, we analyzed the relationships between NPPD and T₀, P₀ (the sum of the daily temperature above 0℃ and precipitation in 2010, respectively), T₁₀, P₁₀ (the sum of the daily temperature above 10℃ and precipitation in 2010, respectively), T (the average temperature in 2010), TT (the average diurnal temperature difference in 2010), P (the average precipitation in 2010), PP (total amount of precipitation in 2010), S (the total hours of sunshine in 2010), and the consumption of chemical fertilizer in 2010. The results indicated that all the factors considered could influence the distribution of NPPD; however, the most influential factors varied among the 9 regions.