Using the Doppler weather radar data,this paper studies a rain and snow weather process occurred in Jiangsu province from 21 to 23 December 2004, and analyzes the variation characteristics of base reflectivity field,base velocity field and vertical structure of wind field and divergence field in the precipitation system in the process of development of precipitation.The results show that adjustment of wind field in the precipitation cloud often predicts the variation of rain, and the change of dynamical structure of precipitation system is associated with the evolution of precipitation.