There has been worldwide concern for sustainable development especially after the 1992's Rio's UN Conference on Environment and Development. Rapid encroachment of urban development on valuable agricultural land will have great influence on whether sustainable development can be achieved. A sustainable land development model is developed using GIS in an attempt to control urban sprawl under rapid rural urbanization. The objective of the model is to ensure that equity between generations and efficiency in land use can be achieved in land development so that development can be sustained in the future. The model is used to study the impacts of agricultural land loss in Dongguan in 1988-93, a rapidly growing area in the Pearl River Delta of China. The impact of unplanned urban growth is evaluated by comparing the actual development with optimal development derived from the sustainable land development model. Land use problems are identified in both spatial and time dimensions as some land conversions are found to occur at the ‘wrong' time and locations. Future land development which can meet the objective of sustainable development is proposed using the model. By testing different development scenarios and land consumption parameters, planners and government officials can use the model as a decision support system for sustainable land development in areas in the world that are under great pressure of rapid urban growth.