The three-dimensional structure of two landfalling typhoon,Jelawat and Bilis(2000),during their formations is discussed based on the NCEP/NCAR global tropospheric 1°×1°analysis,using tangential average wind profile,vertical velocity and potential vorticity.The results show that during the typhoons’ formation,the radius of maximum wind decreased with increase in maximum wind velocity,and the vertical motion initially developed in the mid-troposphere gradually enhanced and expanded to the upper and lower levels,simultaneously.On the other hand,the positive potential vorticity gathered gradually over the typhoon center,and the physical variables changed more obvious at 850hPa and 500hPa than 300hPa.