In this paper, the dynamic characteristics of typhoon Goni, the No.9 typhoon of 2009, were analyzed with the threedimentional grid reflectivity generated by Cinrad Mosaic System developed by the State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences and the wind field retrieved by a twostep variational method proposed by Qiu［27］. The main results show that: (1) Horizontal component of wind retrieved by the twostep variational method demonstrated the vortex structure of typhoon Goni very well. The tangential component of wind was of unsymmetrical distribution with wavenumber 1; (2) Within the radius of maximum wind (RMW), the mean tangential component of wind increased linearly according to the increasing distance away from the center of Goni at the height of 4 km, and quite nearly the famous Rankine vortex model［31］; (3) The inflows did not run into the center of Goni at all azimuths at low levels and at upper levels the outflows did not run out of the center of Goni in all directions, either.