With the utilization of FNL reanalysis data, the Temperature of Black Body (TBB) observed by FY2H satellite as well as dualpolarization radar base data, a diagnostic analysis of three warmsector rainstorms occurred in Zhejiang Province in late spring and early summer of 2020 (shorted as “5·25”, “5·29” and “6·2” process respectively) is conducted. The results show that: (1) All the three rainstorm processes occurred under the background of the lowlevel shear line in front of the upper trough. However, the depth of the upper trough, the position of the mesoscale shear line, and the abnormally strong southwest jet pulsating together caused the varying precipitation area and intensity. (2) The rainstorm area deviated from the west side of the wet Qvector convergence. The negative value area of the wet Qvector divergence field at 700 hPa was a good indicator for the rainstorm. (3) There was frontogenesis with a pair of temperature advection centres when the rainstorm occurred. The middlelevel frontogenesis occurred before the low level, and there was a weak temperature advection during the “5·25” process, with shorttime heavy rainfall and low precipitation efficiency. In comparison, the “5·29” and the “6·2” processes both had strong temperature advection, along with longlasting, heavy rainfall and high precipitation efficiency. (4) The rainstorm cloud of “5·25” had a small scale with a short life cycle, and the precipitation was relatively stable, while the cloud was dense. The centroid height of the strong echoes was lower during the “5·29” process, which was biased towards a kind of mixed precipitation dominated by cumulus clouds. However, the centroid height of the strong echoes was higher during the “6·2” process, with αmesoscale convective clouds, large scale cold clouds and columnar echoes, mostly cumulus precipitation.