Factorial ecological analysis is used to reveal the residential spatial structure in Metropolitan Toronto in this paper. The first result Obtained from a principal components analysis of 32 variables across 136 samplecensus tracts shows that family status construct, ethnic construct and occupation construct are major factors causing urban residential differentiation. The second result obtained from a cluster analysis indicates that the family status is of concentric pattern, the social-economic situation sectoral pattern and the ethnic group both concentric and sectoral pattern. The mechanism forming the model includes the motive force of the city development, the land value rule and the zoning bylaws of city administration, and the demand behavior of household.