Abstract: Track variation of severe tropical storm “Vongfong” is analysed by using radar images of 6 min interval, satellite and conventional data during landing. With the distribution of moisture convection concerning the storm center, which are observed from radar and satellite images, and complete form of vertical vorticity equation containing diabatic heating, the influence of vorticity increasing and vorticity advection caused by moisture convection upon the track of storm is discussed, and a possible reason of track variation during landing is explained. It is considered that the reason of high speed and more westering component moving was the northwestward vorticity advection due to strong moisture convection locating in the northeast to north region of the storm center during the pre-landing period, and the reason of low speed and northwestwards moving in the first 3 hours and northwards in the late 3 hours was the strong moisture convection locating in the west region in the first 3 hours and locating in the south region in the late 3 hours during the landing period, and the reason of high speed and northwestwards moving was the moving tendency to the strong convection locating in northwest region because of the storm rapidly weakening and the strong convection briefly maintaining only in the southeast to northwest region during the late landing period.