The rural settlements accounted for a great proportion of overall building land in China, but it still expanded in recent years along with urbanization and gradually decreasing rural population. To explore the reason for this phenomenon, an analy-sis has been made based on the investigation in a traditional agri-cultural region. This study found that socioeconomic factors, in-cluding the scale of families and its quantity, the improvement of rural public infrastructure, the change of population and the pres-sure of arable land, have effects on the expansion. The view on land tenure which has shaped in farmers minds in the long haul makes them dispose their houses cautiously, and this was the main cause of the fact that one household own more than one plot. In addition, the limitations of rural land institution are unconducive to inspiriting the transfer of farmers' building land and redevel-opment of the idle housing land.