At present, more and more rural- urban migrants purchase urban houses in China. Studies on the floating characteristics of purchasing urban housing for a permanent home and deeply understanding the direction and difference of rural-urban migrants might help to know public migration intention from the demand side. Furthermore, relevant policies of urbanization and citizenation could be better formulated from the supply side. In this study, 1327 valid information from China's 24 provinces and autonomous regions such as Jiangsu, Henan, Shaanxi and so on was collected through random questionnaire survey of farmers, migrant workers, undergraduate students, graduate students and their family members. Basic situation of rural-urban migrants and their family members of purchasing urban housing were filled out by participants' memories or telephone inquiries. Floating characteristics of rural- urban migrants for purchasing urban housing were summarized by data analysis. Furthermore, causes and formation mechanism of floating direction differences were probed into from the perspective of individual or the family by spearman bivariate correlation analysis and multiple classification logistic regression analysis methods. The results show that firstly, few rural-urban migrants purchased urban housing during the 1980s-1990s, whereas migrants of purchasing urban housing have been gradually growing since 2000 and tend to be younger. What's more, migrants of higher education level purchase housing in the cities of larger scale or higher grade in general. Secondly, cities within the province or autonomous region, especially, county-level cities are the main destination of rural- urban migrants purchasing urban housing, and the attraction of town is weak as a whole. It can be seen from the data that the original location of migrants affects the floating orientation of purchasing urban housing, namely, rural households of ordinary township move to the county-level cities and towns nearby, but the households near big cities specially provincial cities prefer to purchase their housing in those higher-level cities. Thirdly, cities and towns of different levels in the eastern provinces, compared with the other regions, take a relatively larger proportion of purchasing housing, and from the whole country, towns take the largest percentage. These indicate there exists the relatively developed regional economy and the urbanization pattern of coordinated development among large, medium and small cities and towns; Rural-urban migrants dispersedly purchase their housing in cities at or above the county level in the central provinces, where the county-level cities and cities of other provinces at prefecture level and above have the largest proportion of purchasing housing among the three regions. The urban housing of rural-urban migrants in the central provinces is decentralized; In the western provinces, migrants who purchase their urban housing in the cities of prefecture level and above account for more than half, and the proportion of migrants flowing to towns by purchasing housing is the lowest among the three regions. These reflect that it is still underdeveloped and unbalanced inside. Finally, it should say that it is the interaction between the urban and rural demand, the interference of other cities and the distance to the city that influence spatial distribution of migrants for purchasing urban housing. Moreover, the desired economic income and the attraction of the city should be the underlying causes that migrants purchase the urban housing in the cities they work. People prefer to choose the housing in the county-level cities and towns of their hometown or the higher levels of cities nearby if they do not have the stable work in the cities. Through the quantitative analysis we also found that the floating differentiation between migrants for purchasing urban housing is significantly correlated with the personal or family factors such as education degree, fixed job or not, work in the city of purchasing the housing or not, work time in the current city, the age of buyers, and so on. In a word, the social environment and policy implications at the macro level, all media's role of the urban and rural system at the middle level and the subjective behavior of individual or family members at the micro level comprehensively drive the spatial differentiation of rural-urban migrants. © 2016, Science Press. All right reserved.