The intensity change of typhoon Mindulle landing is studied. First, the structure changes during typhoon Mindulle landing at Taiwan and Zhejiang provinces are analyzed with the radar echo data. The result shows that Mindulle seems loose during its first landing but has become more organized during its second landing. The enhancement of Mindulle is proved further by the rain belt distribution and the vorticity distribution on the surface,which are calculated with the data of automatic meteorological stations in Zhejiang Province. At last, the vapor and baroclinic energy conditions during two landings are analyzed with the NCEP reanalysis data. It shows that the main reasons for ‘Mindulle’ to enhance during the second landing are the vapor transport from oceans, and the intrusion of cold air from the north.