Abstract: Intensive observational studies on clouds and precipitation have been conducted in the project of the Third Tibetan Plateau Atmospheric Scientific Experiment. In order to further reveal cloud microphysical structure, water transformation in clouds and regional water budget properties over the plateau, a relatively typical convective precipitation process on July 5-6, 2014 in the Naqu region is investigated using mesoscale numerical prediction model (WRF) combined with observational data collected during the experiment. The results indicate that WRF model could reproduce the general characteristics of cloud process and diurnal variation of precipitation over the plateau. The modeling results show that there were large amounts of supercooled cloud water and graupel particles in the summer convective clouds over the plateau. The ice process played a critical role in the development of clouds and precipitation over the plateau. The surface precipitation mainly formed by the melting of graupel particles. Although the warm cloud microphysical process had small direct contribution to the formation of surface precipitation, it had an important contribution to the formation of graupel embryos. The accretion transformation process of ice crystal with supercooled raindrops contributed to the production of graupel particles and its growth mainly relied on the riming process for supercooled cloud water. The net water vapor budget was positive at Naqu over the plateau and the mean daily conversion rate from vapor to precipitation was as high as 20.75%, which is close to that in the downstream of the Yangtze river and higher than that in northern and northwestern China. The contribution of daily mean surface evaporation to precipitation, i.e., precipitation recycling, was 10.92%, indicating that 90% of the rainfall was from the conversion of water vapor outside, although local evaporation of water vapor had a certain contribution to the water vapor source of the rainfall over the plateau.