Based on the conventional high-altitude and surface observation data, NCEP/NCAR reanalysis data and radar data, this paper analyzes the mechanism and evolution characteristics of convection initiation under the influence of cold air in Suizhou and Jingzhou areas of Hubei Province on 4 May 2020. The results show that there were three initiation processes of severe convection in Suizhou Area, including warm sector convergence process, cold front process and low-level jet process. At the same time, the special topography of Suizhou played an important role in the maintenance of severe convection. The condition of convective initiation under the influence of cold air was related to the thickness of cold air and the level of free convection. When the convergence level of cold air and warm moisture flow was higher than the free convection level and the convergence had a certain vertical thickness, convection initiation was more likely to occur. The cold air intensity in Suizhou was stronger than that in Jingzhou, and the front at lower tropospheric level was strong, the updraft in the middle and east area of the positive potential vorticity anomaly was strong, which favored convection initiation. However, there was no convective initiation in Jingzhou, because the lower tropospheric front was weakened, and the cold air and updraft were also weaker.