The article analyzes the situation of urban growth after the establishment of the PRC.It also discusses characteristics and contributing factors of urban size distribution in the three regions and probes into negative effects caused by drawbacks of urban size structures in the Middle Region and the West Region on the policy of opening to the world and the development of the western areas.The article indicates contradictions between the policy of "controlling the size of the large cities", the policy of opening to the world, the establishment of the system of socialist market economy and the strategy of the development of the western areas.The article shows that large cities are "growth pole" in the regional economic development.Because of lacking large and super-large cities in the Middle and Western regions there will be fewer opportunities for making innovations and being in the lead in these regions.It will impede the successful implementing of the strategic development of the Western areas.