Using radiosonde and ground mapping data from conventional observations， FNL analysis data （1°×1°） and quality controlled hourly precipitation data of Yunnan regional automatic station， diagnosed the function of the Qinghai-Xizang Plateau’s eastern slope topography in the PLV （plateau vortex） affected precipitation in Yunnan during 2-3 July 2017.While the latest WRFv4.0 numerical model is used to conduct the topographic sensitivity test of this process.The results show that PLV which generated in the Yajiang region of Sichuan province （NO.C1735） is an important system influenced on this heavy rainfall in Yunnan； This low-vortex system maintain warm core structure in the middle and high altitude during the process period， corresponding with remarkable alternately distribution of ascending and descending movements； Distribution of process accumulated rainfall present two obvious NW-SE rain belts parallel to the mountain trend and the precipitation on the rain belt have intensity interlaced fluctuation characteristics； The heavy rainfall mainly occurred within two periods： one from afternoon to evening and other at the first half of the night， and all located besides the terrain slope （the east and south slopes）， especially in areas with steep terrain， large slopes， and trumpet-shaped topography， and then propagates downstream alone with the PLV； The South Asian High， northwest divergent airflow， Western Pacific subtropical high and Yunnan-Myanmar high provides favorable upper flow field for the eastward movement and development of the PLV， besides the position of 500 hPa positive vorticity and 700 hPa water vapor flux convergence can well indicates the heavy rainfall area； There exist β-mesoscale gravity wave during the period of precipitation， which stimulated by the Qinghai-Xizang Plateau’s eastern slope， and propagate between 300~200 hPa； Non geostrophic equilibrium motion and vertical wind shear at high-altitude are beneficial to the occurrence and propagation of gravity wave； The gravity wave propagate downstream before the PLV and precipitation， its wave ridge corresponds to the upward motion and divergence center， whereas the wave trough corresponds to the descending motion and convergence center， the heavy precipitation and the wave ridge are all located at the southwest side of PLV， the area of strong convergence and upward movement； After reduced the terrain height， its mechanical blocking and lifting effect weakened， the gravity wave and PLV disappears， leading to significant changes in the intensity and spatial distribution of the rain belt； Thus， the topography of the eastern slope of the Plateau plays important role both on the formation and development of PLV and precipitation in Yunnan under the influence of PLV.