The establishment of an ecological index system for assessment of sustainability of cultivated lands has always been difficult due to lack of long-term cont inuous data of land properties.So usually the assessment results are qualitative instead of quantitative.In this essay an index system for assessment of sustainability of cultivated land is proposed and followed by a case study of Wujiang City, Suzhou City.The index system is divided into three levels, i.e.ecological, economic and social levels.To get a quantitative result in ecological assessment we set up a quasi-basic productivity model and a shadow price model and eliminate the contribution of technique improvement.Besides we assess the economic sustainability and the influence of agricultural policies.