The Tibetan Plateau has an important impact on regional water cycle, ecosystem, disastrous weather formation, and climate change. China has conducted the Third Tibetan Plateau Experiment-Observation of Boundary Layer and Troposphere (2014-2017) Project in order to reveal the physical process of meteorology and atmosphere over the Tibetan Plateau. The observational instruments for cloud and precipitation processes in this field experiment include the C-band continuous wave radar, Ka-band millimetre wave cloud radar, ground-based raindrop disdrometer, lidar ceilometer etc. In this paper, the characteristics of convective clouds and precipitation as well as raindrop size distribution were analysed by using observed data and FY-2E satellite TBB data from July 1 to August 31, 2014. The result shows that the convective activities mainly distributed in the central and southeast part of the Tibetan Plateau and the precipitation had a quasi-two-week cycle during the observational period. Due to the solar heating effect over the plateau, both convective clouds and precipitation processes had obvious daily variation. There were four precipitation peaks in a day, which were 0:00-1:00, 12:00-13:00, 17:00-18:00, 19:00-22:00 (LST) respectively. The convections first appeared at 11:00, and the first precipitation peak happened at around 12:00, which was mainly caused by local thermal convection with relative lower cloud-top height and wider drop spectrum. Then the convections merged and developed to their maximum at 17:00-18:00, during which cloud-base height had a sharp decrease at 17:00 and widest raindrop spectrum and the second precipitation peak happened in this period. At night the precipitation tended to be advective but remained high and lasted until 6:00 and then dissipated. During 18:00-24:00 there was a precipitation peak around 19:00-22:00 and the cloud-top height was as high as that in the afternoon and the number of smaller drops increased. After midnight, the cloud-top height as well as precipitation started to decrease and tended to be more advective, but a forth precipitation peak happened during 0:00-1:00. In the forenoon there were few convections happened. The mean cloud-top height was around 11.5 km (ASL), and its maximum value exceeded 19 km, and the mean cloud-base height was 6.88 km (ASL) during the observation period. Precipitation was mainly short-lasting and showery, and usually lasted less than 1 h, and the mean precipitation intensity was 1.2 mm/h. The result also shows that the raindrop size distribution over the Tibetan Plateau was wider than that over plain at the same latitude and season, because of which the rainfall could be more easily produced over the plateau than that over plain. Rain happened more at night than at noon. However, there were more larger-size raindrops at daytime than at night. Gamma distribution was found to be more suitable for the raindrop size distribution than M-P distribution over the Tibetan Plateau.