Abstract:Daily meteorological observation data of 17 stations and yearly statistical data of Chongqing were employed to diagnose the influence of urbanization on the spatial distribution of rainfall over Chongqing metropolitan region by adopting the method of spatial standardization of precipitation. The results showed that the period of 1970-2009 was divided into two stages by the year 1997, that is the slow developing stage of urbanization and the quick developing stage of urbanization, and spatial difference of annual rainfall over the metropolitan region has relations with the acceleration of urbanization. Comparing the difference of the two stages, it is found that with the fast development of urbanization, the annual rainfall amount, rainfall intensity and the frequency of moderate and torrential rains has got increased, showing the distinct feature of urban “rain island”. In addition, as far as seasonal difference is concerned, urbanization has exerted different influence on spatial distribution of precipitation over the metropolitan region in Chongqing in summer and winter. The urban areas and the suburb in the north of the city see more rains over summer time while the increase of precipitation happens in the urban areas and its suburb in the south in winter. Such spatial distribution of rainfall in different seasons is possibly caused by the interaction between seasonal prevailing wind and the temperature gradient of urban areas and suburbs so that the rainfall in the urban and its downwind areas has increased significantly， especially in the downwind areas.