Using the data of the Second Tibetan Plateau Scientific Expedition and numerical simulation results with five-nested domain and high resolution of 333m of WRF model, the role of local mountain-valley wind circulation in an orographic clouds and precipitation event on 17-28, September 2019 in Nyingchi region of southeastern Tibetan Plateau is investigated. The results show that the precipitation event was caused by a passage of westerly trough and Nyingchi station is located at the base of westerly trough with weak unstable stratification. The orographic clouds and precipitation event is found to have obvious three-stage variations in the afternoon, evening and night, and the local mountain-valley wind circulation has an important role in the variation. In the afternoon, the strong solar radiation heating forms obvious upslope winds in the sunny slope firstly, and produces the strong upvalley winds, which are blocked and lifted in the windward slope, and induces strong mountain waves, and strong convective clouds and precipitation. In the evening, the strong longwave radiation cooling forms obvious downslope winds and cause the convergence and lifting process of warmer air in the valley, enhancing the formation and development of weak convection and stratiform clouds on the valley. In the nighttime, the downslope winds reach the strongest, and downvalley winds (mountain winds) are further enhanced, and the strong lifting causes deeper stratiform clouds. The convective clouds in the afternoon have more graupel particles and the main rain sources are from warm rain and graupel melting processes. The snow is very few. However, the similar cloud microphysical properties can be found in the evening and nighttime, the snow become dominant and the main rain sources are from snow melting and warm rain processes.