Abstract: Since the reform and opening up,China’s economy has been continued to grow,the process of urbanization in China keeps being accelerated,and the income gap of urban residents is widening.Along with the demolition of the original urban housing,the passive relocation of the urban residents,the pluralistic social groups are reconstructed in the diverse urban space and commodity communities.The role of sorting and filtering on the urban residents leads to the same social stratum tends to live in the same space,the phenomenon of different social strata forming heterogeneous living space,resulting in the differentiation of different social groups in the living space.As a result,the degree of differentiation of social strata needs to be examined from the perspective of geography.In order to analyze the spatial differentiation of urban social strata,taking Lanzhou City,Gansu Province,China as an example,this paper discusses the differentiation of urban social strata brought about by income gap as well as the degree of differentiation of urban social strata mapped in residential space.The data of commercial housing in Lanzhou were obtained by means of network crawler tools.The geographical distribution characteristics and spatial differentiation degree of residential strata were studied by using Reardon spatial differentiation method.The results show that: in terms of the geographical distribution of residential-social strata,Chengguan District and Qilihe District show a circular distribution of elite,wealthy,middle,low and poor groups from the center to the periphery.But there is the phenomenon of “invading” low-grade residential circle in elite area; the distribution of residential-social stratum in Anning District and Xigu District is complicated,with mainly middle-middle class,low-middle class and urban village-poor class,and tends to a mixed distribution,and the marginalized characteristics of the village in the city are remarkable.In the aspect of spatial differentiation of residential-social strata,the rich-class residential areas are more inclined to merge,and the low-class residential areas have the tendency of differentiation.The residential-social class differentiation in Qilihe,Anning and Xigu Districts is obviously higher than that in the Chengguan District with the characteristics of the isolated elite class,the fusion of the rich and middle class,the tendency to separate the low-yield and the poor class;The difference between residential and social strata in the urban center is lower,and the degree of differentiation from the edge is higher,showing the discontinuous structure of the circle.The spatial differentiation of residential-social strata becomes more significant with the decrease of the research scale,which indicates that the spatial differentiation in macro-scale will lead to different research results due to the different measure scales,and the spatial differentiation in macro-scale has a significant weakening phenomenon.Micro-scale can reflect the objective reality of spatial differentiation.

Key words: residence-social class, social differentiation, spatial entropy index, Lanzhou City