This paper analyzes the coupling mechanism between urbanization and eco environment: the intimidation on eco environment from urbanization is caused by contamination from population, enterprises and transportation; Meanwhile, the restriction against urbanization from eco environment results from changing the flow direction of population and capital. On the basis of the above, the authors deduce the coupling function and theshape curve between urbanization and eco environment in two ways: algebra and geometry, and then opens out the relationship law: regional eco environment decays at first, and thenameliorates after the curve inflexion. This paper also discusses the coupling process of urbanization and eco environment, andclassifies it into four stages, whichare low level coordination stage, resisting stage, ameliorating stage and harmonious stage. Finally, the authors demonstrate the coupling relationship between urbanization and eco environment in Zhejiang province, and points out that industrialization is still the main momentum of urbanization in Zhejiang.In spite of the emergence of partial inflexion in the coupling curve between waste water and urbanization in Zhejiang, becausethere is no complete conversion in industrial structure, once policies concerning environmental protection change, the coupling curve between eco environment and urbanization will fluctuate. That is to say, Zhejiang is still at the resisting stage.