Abstract: Based on surface precipitation observational data, NCEP/NCAR FNL reanalysis data, ECMWF model prediction field data and FY-2 H geostationary satellite TBB data, the present study analyzed a rainstorm process in Zhejiang Province on June 30, 2020. The results show that: (1) Favorable conditions for the process include the strong upper-air divergence of the 200 hPa South Asian High, the eastward movement of the low trough in the middle latitudes, the stable blocking of the subtropical high, and the cold shear formed by the intersection of the cold air and the warm and wet air at the back of the Changjiang River-Huaihe River Cyclones (Jianghuai Cyclones). (2) The expansion area of water vapor flux in the mid-low troposphere and the vertical helicity at 700 hPa are both good indicators for heavy rain. The positive water vapor flux divergence at the upper troposphere is stronger than the negative one at the lower troposphere. The vertical helicity and the vertical velocity center almost coincide. The strong lowlevel convergence followed by the strong vertical upward movement provide good water vapor and dynamic conditions for the rainstorm. (3) The rainstorm area is located near the transition zone of the positive and negative value of MPV, MPV1 and MPV2. This zone is also the conjoint area of convective and baroclinic instability. The region in which the isentropic of θse densely distributed is almost perpendicular to the ground. The high-altitude cold air flow drives the high-potential vortex to the lower level, causing regional severe convective rainstorm. (4) The precipitating cloud near the cold shear line at850 hPa has been consolidated from multiple massive convective clouds into a completely banded cumulonimbus cloud, and newborn convective clouds move eastward continually from the upstream, forming a significant"train effect".