Abstract: The dramatic institutional and spatial transformation has brought great challenges for the planning and provision of public housing and transportation in terms of social sustainability. In the western cities, the urban disadvantages such as the female, the elderly, the disabled, and the low-income groups have been "entrapped" in certain spatial territory with lower level of accessibility and mobility in their daily life as a result of the urban sprawl, suburbanization of jobs and other public facilities, the institutional housing segregation, as well as the deficiency of the public transit. In China, there have been great social transformation and spatial restructuring driven by the dissolve of Danwei compound, land use separation, industrial suburbanization, and residential relocation during the process of market-oriented transition. As a consequence, individuals, especially the urban middle and low-income groups, would face great challenges of decreasing accessibility and mobility in their daily life which could in turn result in the decline of the life quality. Aiming at discovering the spatio-temporal demand of the urban middle and low-income groups and promoting the social equity in urban policy and planning, this paper explores the spatio-temporal activity pattern of the urban middle and low-income residents in Beijing from the perspectives of the temporal allocation and spatial distribution of both work and non-work activities, observed daily activity space and mobility based on the activity diary survey of 600 households, 1 119 individuals of Beijing in 2007. Aided by the GIS technique and tools, the 3D geovisualization of individual's spatio-temporal path and the spatio-temporal activity density surface are introduced to explore and compare the spatial and temporal pattern of the middle and low-income groups and their counterpart group. It is found that the social transformation and spatial restructuring in urban China has exerted obviously more negative impact on the daily life of urban middle and low-income groups than their other groups. Firstly, the whole daily activity pattern show the trend of "fragmentation" due to the existing of large amount of out-of-home, non-employment activities during the day time. Also, the middle and low-income have relatively shorter work hours than their counterparts in the workday while they have relatively longer work hours than their counterparts in the weekend. Secondly, there is no strong rhythm of their work time, and their work activities relatively dispersed in the large spatial extent. Also, most of their non-work activities are located within the 1-km distance from their home. Thirdly, the middle and low-income group has lower level of mobility than other groups. They have more single purpose trips, and more frequently use the non-motorized mode such as walk and bicycle in their daily life. Besides, they have much smaller observed activity space measured by convex polygon. Finally, it is argued that much more attention should be paid to the accessibility and mobility consequences of provision the public housings for the low-income group.