Based on the analysis of succession processes of agroecosystems,this paper puts forward the conceptual framework for the development trend of agroecosystem's sustainability which embraces the inter year coefficient of variation,the rate of change in temporal development slope and the initial threshold level of assessment indicators.The study of Deqing County, as an example,indicates that the county's coefficient of development trend of agroecosystem's sustainability is 0.657,being at the middle and upper l...