The Measure Of Urban System Niche

China’s urbanization has entered a critical developing period, Under the appearance of our changing urbanization rate; there is a lot of issues which urban construction and sustainable development are not uncoordinated, leading to low quality of urbanization in many areas. It needs new ideas to guide sound and rapid advance of urbanization. Just as natural ecosystems, city (town) has its own formation, development, rise and fall. Urban System includes central urban area which is the core of the inner city, countries and villages which is the aid of the system, and they have their own roles in the system. The niche of each city is based on the objective existence of their own interaction with the environment; it describes the relative position and relationship between downtown and town in time, space, resources. Urban system is characterized by multi-dimensional. The county towns must clearly evaluate their own position, strengths, weaknesses, in order to clear the direction of development and then achieve the sustainable development of the urban system.This article focuses on the ecological formation law of urban system and the dynamic mechanism of development of urban system, evaluates the niche of the Kunming Urban System as a example, analyses the urban development based on the results of the evaluation, in order to optimize the niche Within the urban system. First of all, the meaning of the Urban Niche is generalized and the point of Niche Theory is elaborated by the way of literature review and theories reorganizing, Combined with current situation of China’s urban development. Next, formation law of the urban system is analyzed combined with the features of Niche Theory and urban system and urban system’s dynamic mechanism of development is analyzed from two angles of the internal forces and external forces. New concept of compact urban planning is used for reference to optimize the urban problems caused by pole pit development stage. Third, a niche evaluation index system is built which includes four dimension as basic dimension, life dimension, economic dimension and nature dimension. The scope of the study is Kunming urban system, and Entropy method, Niche Theory is used to estimate the consolidated Niche and dimensions Niche of all county towns in the urban system. Physics gravity model is used for reference as an empirical model to estimate the radiation ability to surrounding county towns of central urban area. The developments of Kunming urban system is evaluated intuitively. the consolidated evaluation results Kunming urban system shows that Kunming urbanization quality is low; The gap in terms of economy or society is significant between central urban area and county towns; The overall performance of county towns is unitary; Driving effect of the central urban area is not strong enough; Kunming shows a trend of south rich and north poor; Because of lacking nature resources central urban area is under high pressure, on the other hand, the county nature resources are not in full use.