In this paper, the mesoscale characteristics of rainstorms in Shandong caused by Typhoon RUMBIA in 2018 areanalyzed by using 3-D radar mosaic technology based on data of Doppler weather radar, regional automatic meteorological station, conventional observation, and NCEP reanalysis. The results show that the rainstorms in Shandong caused by Typhoon RUMBIA have great differences in the characteristics of rain intensity at different stages, and the sustained heavy rainfall is a main factor causing the disastrous rainstorms; the rainstorm clusters of this typhoon have strong moving characteristics and the formation of train effect is an important factor causing the disastrous rainstorms; the 3-D radar mosaic data can clearly identify and analyze the movement, merging, and development of mesoscale rain clusters during rainstorms, which is very important for accurate monitoring and forecasting of rainstorms.