Abstract:A Jianghuai cyclone which caused regional severe torrential rain in East China and extreme precipitation events at several stations in Jiangsu Province during 9-10 June 2017 is analyzed based on NCEP 0.25°×0.25° reanalysis data and multiple observation data. The generation, development, front structure and equivalent barotropy are studied by comparing with another Jianghuai cyclone with less precipitation. The results are as follows. (1) The divergence caused by positive vorticity advection and distributary at upper troposphere led to the generation of the “0609” (9 June 2017) cyclone while the warm advection at lower troposphere triggered the “0605” (5 June 2017) cyclone. (2) The calculation of frontogenesis function indicates that frontogenesis was much intenser in the “0609” cyclone than the other which made the frontal surface less tilted and the upward motion in warm area much stronger and deeper. These factors and the slow motion of front could be the direct reason for the regional torrential rain. (3) Vertical profile of relative vorticity and 0 contour of zonal wind indicates that the “0609” cyclone had an intense vorticity column and vertical structure below 700 hPa, which made itself some equivalent barotropic, while the “0605” cyclone had a tilted structure and it was more baroclinic. (4) The latent heat released by intense precipitation could strengthen the cyclone by mixing vorticity and the strengthened cyclone could enhance the precipitation conversely, creating a positive feedback mechanism like CISK between cyclone and its precipitation. This could be the reason for the equivalent barotropy of the “0609” cyclone, showing the multiple evolution pattern of Jianghuai cyclone.