This paper firstly analyzes Guangzhou social area structure in 2000, and then compares the results with the structures in 1985. Its purpose is to study the social area change law of Guangzhou during economic system transformation, and to conclude the general social structure model of metropolis in China. On the basis of Principal Components Analysis and Hierarchical Cluster Methods, this paper processes more than 200 variables related to the social area structure from the fifth census data of 2000, and gets 5 key factors of "the degrees of population density", "the education level and occupation", "family status and the proportion of farmer population", "the proportion out of work", "the quality of apartment" who influence Guangzhou social area structure, and divides Guangzhou city into 7 kinds of social areas, that is "the densely populated, crowded old city area", "the residential area of medium-sized income stratum", "the residential area of salary stratum", "the residential area of the intellectual, advanced job person", "the mixed residential area of the migrant and local people", "the urbanized residential area in the suburbs", and "the farmer residential area". After comparison with the social area pattern of Guangzhou in 1985, this paper finds that Guangzhou social area has the following changes from 1985 to 2000: (1) the main factor influencing social area change is still "urbanization" although the importance of "social status" is getting high; (2) the social area structures get more complex, and the income gap and migrant population play a more important role in the formation of social areas; (3) and the three change patterns of Guangzhou social areas are concluded, that is the change pattern based on old city area, the one based on manufacture or university enclave and the one based on farmer social area. Finally, this paper analyzes the mechanism of the social area change from the point of view of national policy change during the economic transition, the history of city growth and the planning control of the government, then outlines the pattern of social spatial structure of China's cities during the period of economic transition, explains the differences of social area structures in China and in Western countries, and predicts the future changes of Guangzhou social areas based on occupation splitting up, family life cycle and migrant population.