Based on RS data, statistical data and field investigation, the paper analyzed farmland changes and its driving forces in Daye City from 1991 to 2000 by combining the methods of qualitative analysis with quantitative analysis from 3D perspectives, namely, functional mechanism of natural environment, the orientation mechanism of socio-economic development, the decision-making mechanism of community groups and individuals. The results showed that ①In terms of natural environment, the intersecting regions between the mine and agriculture, lake and land, agriculture and the forest were the major origins leading to natural disaster in Daye City; ②In terms of socio-economic development, the transformation from planting-based industry to comprehensive development of agriculture, animal husbandry, fisheries in the field of agriculture, the pattern of township-industrial-oriented development in the field of industry, and the "false" urbanization of population were the basic characteristics; ③In terms of social groups and individual decision-making, the impulse of local governmental investment and land expansion accelerated the conversion of farmland to construction land, it wasn’t harmonious with the needs of economic development in Daye City. Governmental policy of returning farmland to forest or lake, farmers decision on economic interests-oriented had a dominate position in the adjustment of the agricultural structure. Finally, this paper pointed out the control measures to sustainable farmland use in Daye City.