Abstract:MICAPS (Meteorological Information Combine Analysis and Process System), CIMSS (Cooperative Institute for Meteorological Satellite St udies) and satellite data are used to analyze the rapid increase in Typhoon Khanun (0515) intensity before landfalling. The results show that the heat flux divergence caused by the movement of the upper trough, the increasing southeast air flow and the deceasing vertical wind shear are the main reasons for the rapid increase in Typhoon Khanun intensity before landfalling.