中文摘要：

国内特大城市大多采取多中心空间战略，但效果并不明显，其理念的有效性尤其是经济的有效性需要严谨检验。尽管主流经济学对此还没有完整、精确的答案，但城市经济方面的研究成果却给出了方向性的结论，即随着城市规模扩大，集聚的负外部性产生的成本会逐渐超过规模经济带来的效益，最终导致单中心向多中心转化。这一结论从经济绩效角度为多中心的规划理念提供了理论依据。实践中的多中心战略之所以达不到预期效果，原因在于城市经济模型是基于自由市场机制的前提假设，而这与现实存在很大出入。为了降低由多中心结构形成的时滞性造成的城市利益损失，政府应发挥作为城市整体利益最大化代表的作用，在尊重经济运行规律的基础上及时做出空间转型的决策，并发挥政策聚焦和资源调动优势，促进外围有初始优势的地区迅速发展成为次中心城市，积极主动地推进多中心空间结构的形成，从而实现城市空间布局的最优化和城市整体利益的最大化。

英文摘要：

The polycentric spatial strategy has been applied in many mega-cities in China recently, but has seldom reached its expected effect. Hence, the effectiveness of the polycentric idea, especially its economic performance, needs to be examined. Urban economics theories suggest that the increasing cost stemming from agglomeration diseconomies may exceed the benefit resulting from agglomeration economies gradually when urban areas expand. Finally, the monoentric structure will transform itself to the polycentric one. This conclusion provides clues to polycentric planning in real practice. However, polycentric strategy usually cannot reach the expected result in the real world because free market hypothesis can be unrealistic. To reduce the loss of urban efficiency caused by the lags in the urban polycentric formation, the government should respect market rules, to take full advantage of its role in resource mobilizing, and to promote advantageous urban fringe areas.