The FNL grid data from NCEP (National Centers for Environmental Prediction) are utilized to analyze an explosive cyclone process occurred in the northwestern Pacific Ocean from 11 to 13 January 2012.The Weather Research and Forecasting model (WRF) is employed to simulate the explosive cyclone from 1800 UTC 10 to 0000 UTC 13 January 2012.The cyclone breaks out in the east of Japan from 11 to 12 January and weakens near the Kamchatka Peninsula on 13 January after changing direction two times.Results of diagnostic analysis show that there exists a distinct frontal structure in the development of cyclone.The high potential vorticity in the upper troposphere extends downward to the surface,which is beneficial to the development of cyclone.The cyclone develops rapidly along with the formation and development of a low level jet,which leads to more distinct convergence and ascending.Results of SST sensitivity tests suggest that the change of sea surface temperature can obviously affect the development intensity of the cyclone,but it has little effect on the cyclonic path.