For global high-resolution numerical weather prediction, based on the GRAPES developed by China Meteorological Administration, an updated version, the GRAPES_YY, has been developed on the Yin-Yang grid, which is now available at 0.1°×0.1° resolution. The “violent Meiyu” process that took place in the middle and lower reaches of Yangtze River during 6-8 July 2020 is selected as the object of simulation. A case of Meiyu severe rainfall in south of Anhui Province is analyzed by using the 0.1°×0.1° model outputs , FNL 0.25°×0.25° reanalysis data and hourly rainfall observation and weather radar reflectivity. Results show that the severe rainfall was a direct result of eastward moving mesoscale convective systems under the joint action of upper trough, low vortex shear lines and low-level jets. The simulated position and intensity of the large-scale systems is comparable with the FNL 0.25°×0.25° reanalysis results. The orientation and position of the 24 h precipitation are well described in the simulation although distinction on severe-rainfall intensity and weak-rainfall region is found. Persistent severe rainfall depends on the low-level vapor convergence and smooth vapor transport. The severe rainfall is in accordance with the large θse region at 500 hPa, showing up as convectively neutral zone. Except the instable below 850 hPa in frontal zone, convectively instable layer appears at both south and north of the front.