Based on surface automatic observation data, Doppler radar data, Himawari-8 satellite data and ERA-5 high resolution reanalysis data, this paper analyzes the synoptic background, environmental conditions and evolution characteristics of mesoscale systems and convective storms of the EF2 tornado event that occurred in Gaoyou County, Jiangsu Province on 12 June 2020. The monitoring and early warning experience and forecasting thoughts are summarized as well. The results are as follows. The Gaoyou tornado occurred during the first rainstorm process at the beginning of Meiyu in Jiangsu Province. The synoptic condition was partly similar to that of the Funing EF4 tornado on 23 June 2016. The Gaoyou tornado and the Funing tornado both showed up typical characteristics of Meiyu front tornado. The convective system producing tornado appeared in front of 500 hPa westerly trough, in the southwest quadrant of 850 hPa vortex and left side of low-level jet, with strong convective instability energy and low lifting condensation level. But CAPE and vertical wind shear of the Gaoyou tornado were weaker than in the Funing tornado process. The tornado occurred at the top of a moving meso-β scale depression, which was located in the convergence area of surface divergence and the surface temperature warm tongue. The convergence near the center of storm strengthened sharply, which might indicate the tornado. The storm generating the tornado had a long lifetime. Continuous tornado vortex signature (TVS) was recognized 60 minutes ahead. The storm passing through Gaoyou Lake was enhanced. Mesocyclones (M) appeared and coexisted with TVS within 8 radar volume scans. Before the tornado reached the ground, the bottom height of TVS decreased but shear increased significantly. The diameter of the mesocyclone decreased vertically in an inverted trapezoidal structure. The rotation speed shear strengthened, getting to the minimum height. All these features give good indications for the early warning of tornadoes. Based on synoptic-scale system model, meso- and small-scale environmental physical indexes and convective scale storm characteristic evolutions, Jiangsu meteorological departments had a progressive early warning, achieving a successful practice.