Abstract: For the purpose of urban management, many spatial boundaries of urban areas such as administration boundaries, postal zones, urban planning zones, traffic analysis zones were designed by different departments for specific purposes, thus results in incompatible boundaries. The social statistics data based on these zones are difficult to use by other departments due to these incompatible spatial boundaries. The urban basic grid is proposed, and the division principle is detailed. An algorithm based on hierarchical spatial reasoning is designed to delineate the urban basic grid. An experiment is done to delineate the urban basic grid. The results indicate that the urban basic grid can be used to aggregate to higher level urban grid, and thus that the social statistics data collected by the urban basic grid can be shared among other departments.