Abstract:The west and north parts of Beijing are mountainous areas and the urban island e ffect is obvious in Beijing, which can influence the distributions and intensi ty of the rainfall. Using the intensified observation data including wind profil e data, wind and temperature elements of surface automatic weather stations, th e vertical vapor and temperature distributions observed by surface microwave rad iometer, the evolvement and interaction in the temperature, wind and humidity of the Meso β torrential rain occurring in the afternoon on J uly 24, 2006, in Beijing area are studied and it shows how the system cold front is influenced by topography a nd urban island of Beijing， and then the different rainfall centers are form ed. According to the analysis it is concluded that, the cold front influenced the central part of Beijing along a route from northeast to southwest because of the local topography, and when the cold air is obvious the strong rainfall always occurs at the central urban areas with higher temperature. Meanwhile the rainfall center is prone to form in the area of dense anomalous tem perature isolines and in the direction the cold front moves. Wind shear convergence between the southeast wind from the plain and the north wind from the mountains becomes distinct when the cold front arrived near the west mountain, and at the same time the lifting effect of the southeast wind from the plain by mountains strengthened, which is the disturbance cause of the rainstorm. The upward propagation of surface shear convergence is the dynamical support for the rainstor m. The latent heat release changed the temperature distribution during the rains torm, which led to the enhancement of southeast wind which brought vapor to the rainstorm.