Typhoon Fanapi, a super typhoon that generated over the Northwest Pacific and the South China Sea in 2010, is the only typhoon to make landfall twice in China. Intense precipitation brought by Fanapi caused severe damages in Taiwan and in Fujian and Guangdong provinces. In this study, the Weather Research and Forecasting (WRF) model is used to simulate typhoon Fanapi at high resolution (finest grid size of 3 km) with three nests for 120 hours. Detailed comparisons are obtained between observations and the simulation. The results show that the simulation reproduced the development, evolution, and twice-landfalling processes of typhoon Fanapi to a significant degree. The simulated track and intensity evolution are shown to be rather similar to those of observations. Futhermore, the high-resolution simulation data is used to perform diagnostic analysis on the heavy rainfall occurring with typhoon Fanapi. Results indicate that the <|Q|> parameter agrees fairly well with observed precipitation in spatial distribution and time evolution. This parameter shows strong signals over the heavy rainfall region and weak or no signals over other regions; therefore,<|Q|> is an important indicator in the diagnosis of heavy precipitation of typhoons.