Using the Doppler radar data and simulated results of the mesoscale model WRF(Weather Research and Forecasting),this paper studies a precipitation process induced by convective and stratiform mixed clouds in Taiyuan and its surrounding areas during 9—10 May 2009.Results show that the local convection clouds are developed in the formation stage of convective and stratiform mixed clouds.With development and strengthening of the convection,the convective and stratiform mixed clouds are formed in a wider range,by means of merging process between the enhanced convection clouds and the ambient clouds.The merging process includes the local single cells merging,the cloud clusters merging and the high cores merging in convective and stratiform mixed clouds.The single cells merging and cloud clusters merging can bring about the explosive growth of clouds with a sharp increase in graupel content and rain water content.The high cores merging in convective and stratiform mixed clouds can enlarge the rainfall area rather than the rainfall strength.The depression inverted trough and the weak cold font are main influencing factors of formation and maintenance of the convective and stratiform mixed clouds.The depression inverted trough is beneficial to the accumulation of large-range convective energy in the lower layer and the wind shear is favorable to the development and merging of cloud clusters at a short distance.The dynamic and thermal effects of mountainous region promote the formation and strengthening of local single cells and strong centers in the mixed clouds.