Agricultural pollution has become the dominant source of water pollution in China and the carbon reduction in agricultural aspect is pressing. Based on list analysis method, the COD, TN and TP in agriculture in 28 provinces in China from 1995 to 2010 were evaluated and compared. By dint of directional distance function, the economics mechanism to reduce carbon emission was discussed. The reduction efficiency and potential of three kinds of pollutants were estimated. The regression indicates that the educational degree, income level and work play a crucial role in carbon emission.