The research is to study how the difference of economic development between cities is from by observing the change in investment. The different main bodies of investment will make different investment decisions in different stage of life cycle of urban industries. The state-owned units are policy tools, and will invest in urban infrastructure, which is not for profit. In contrast, the only goal of non-state owned enterprises is to maximize the profit, but evade the risk, so they will invest in any profitable items. Finally, the non-state investment will exceed the state investment, and to be more and more important in a city. I select fifty big cities in china to empirically analyze the proposition, and the result indicate that the fixed-investment of non-state sector have exceeded the fixed-investment of the state sector in coastal cities, and the fixed-investment of the state sector is still more than the fixed-investment of non-state sector in inland cities. Under the condition that the goal of government policy is to raise the standard of the infrastructure of inland cities, and that the most industries of coastal cities are staying in industrial growth period, the cities with higher level of economic development grow fast more.