The impact of rapid economic development on the reduction of cultivated land area is one of the hotspots in land-use change researches currently. Introducing STIRPAT model, influence of population, industrial structure and the level of urbanization on the cultivated land changes were analyzed, and the relationship between prosperous level and cultivated land area were analyzed in Suzhou City, using the cultivated land data and related socio-economic development data from 1978 to 2005. The results show that population change is the main cause for cultivated land reduction in Suzhou City since the reform and opening. In addition, changes of the urbanization rate and proportion of the tertiary-industry added value to regional GDP of the area also play an important role in the cultivated land reduction. In the scope of observational data, the relationship between the prosperous level and the cultivated land area is similar to the Environmental Kuznets Curve (EKC), and Suzhou City is at the early stage of the curve, that is, the period of prominent contradictions. Accordingly, several suggestions are proposed in the study to mitigate the pressure of cultivated land reduction, including population control, industrial structure adjustment, urbanization level improvement and economic growth mode transition, etc.