Abstract: The areal structure of cities and towns is concerned with urban features and landuse distribution, as well as with their regularities of evalution.There are three location aspects to identify the urban area. (1) It's as a, terrain type in the whole economic allocation; (2) It's as an areal network in the regional spatial combination. (3) It's as a summation of functional zones in urban areal itself.All the theories and models on urban areal structure were shaped from those aspects,single or multiple, which constitute the spatial economical character of cities and towns.In this paper, the idealized structure of urban areas from the west are introduced. Dispersive group pattern from the socialist countries, the new model of China's urban system and multihierarchical centripetal pattern are fully expounded with living examples.In terms of the genesis of urban areal development, the authors put forward the evolutional law of urban areal structure.It goes sequentially through four stages. (1) Expansion of city or town.;(2) Sprawl of urban area.(3) Formation of centripetal urban system and (4) Appearance of urban continuous belt (megalopolis).This law can be described by some quantitative methods of spatial interaction which are illustrated in detail at the end of the paper.