在关于新型城镇化的讨论中，人口到底如何流动、集聚程度应该为何，是受到热议的话题。从市县层面出发，选取江苏省和浙江省的各地级市作为样本，观察其人口和经济活动是否向市区集聚，亦或是在各个县城分散。随后借鉴已有学术研究观点，从经济结构、经济开放程度和行政力量的强弱等角度，解释样本城市的集聚现象，最后探讨城市的集聚是否能够带来市区经济效率的提升和经济增长速度的加快。,What is a reasonable degree of agglomeration for both population and economic activity is widely discussed in the process of China’s urbanization.This paper discusses the question from another aspect that how population and economic activities distribute in a prefecture-level city, whether they agglomerate in the central city or widely distributed in the counties.We choose prefecture-level cities of Jiangsu and Zhejiang province,test their agglomeration modes of both population and economic activities,and provide some explanations from economic structure,economy openness,administration power and so on. Lastly we test whether agglomeration to central city is helpful to improve economic efficiency and promote economic growth.