Abstract: Regional development gap is one of the key academic issues for economic researchers. Although to some degree it favors to factor flow and resource allocation, long-term and over-huge disparity may weaken the cooperative efficiency between regions. With expanding regional development gap, the way of narrowing the gap has also become the attentive focus of the society. Based on methods of population-economy growth elasticity, center of gravity, geographic concentration and inconsistent index, this paper examines the coordinated evolution law of the population-economy of Yangtze river delta within 2000-2015, and through this perspective explores the driving factors of regional development gap at different periods using spatial panel model. Results show that: the agglomeration pattern of regional population-economy changes responding to the evolution of development environment and policy. The approaching gravity center of pop and economy indicates the gradual narrowing development gap. Economic concentration shows a “Z” shape, while population concentration shows significant north-south difference. Inconsistent index of the population-economy exhibits relatively stable pattern of “core-edge” with the phenomenon of increasing developed cities and decreasing less developed cities, which respectively indicates the significant differences in regional development as well as the evolution of equilibrium trend. Driving factors of regional development gap vary in different periods, overall, the market force strengthens and government influence is weakening. Ordinary panel regression overestimates the effect of many influencing factors, and the declining spillover effects indicates the transition of regional development towards equilibrium. This paper selects one of China’s economic powerhouses-Yangtze River Delta as study area, aiming at offering scientific reference for regional coordinated development.