At the same time,population in the city centers of huge metropolises move out into its suburbs,physical sprawling of several huge metropolises leads to melting and overlapping of their satellite cities or suburbs,thus came into being the megalopolis.

In megalopolis,each metropolitan has linked together by broad traffic and communication,a large variety of population,economic and social activities have concentrated,and plural urban system has formed,which promote megalopolis becoming the hinge of social and economic system in America,meanwhile,an "incubator" of new trend in urban evolution.

However, there are other similar concepts including metropolitan area, metropolitan interlocking region and urban agglomeration, etc.

Taking the metropolitan interlocking region in Yangtze River Delta as a study case, this paper analyses problems existing in the process of tourism urbanization, such as .

Against this background,the paper defines and analyses several concepts,such as cities group,urban agglomeration,city-and-town concentrated area,metropolitan district,metropolitan interlocking region,megalopolis and so on,especially .

The Boundary analysis of megalopolis contains mainly the whole spatial boundaries and the inter- nal structure boundaries.

The rapid development of the regional urbanization has transformed this area into a megalopolis.

Based on the experience of international megalopolis,authors of this paper considered that influential factors of population capacity of the Yangtze River Delta are industry assembling scale,resource support ability and environment capacity.

With the metropolitanization in US in the early 20~(th) century,Megalopolis represented typically by the Northeast seaboard Megalopolitan area in US emerged.

Through a study of the characteristics of the urbanization in the Zhujiang River Delta in recent years and its future developing tendencies and also in a comparison with such concepts as exo-urbanization urban belts urban districts urban regions and urban agglomerations etc.