Abstract: The paper makes judgment about convergent tendency on the basis of estimating the whole gap of economic development in Yangtze River Delta. Based on the related theories of spatial economics, it also analyzes the reasons of differences or changes during cities’ development with gauging models. The analytic result shows that the whole gap of economic development in Yangtze River Delta is reducing gradually in recent years due to some important influencing factors such as investment in the fixed assets, capacity for macro-control of the local governments, extent of opening-up and so on.