Based on the analysis of the Features with the physical quantities of the relative parameters 5 days before the explosive development of the cyclones over the Northwest Pacific in winters during 1975-1988,it is found out that the locations of the explosive cyclones are related with the disposal of the ultra-long wave,long wave and the location of the westerly jet center in the middle-up troposphere. The studies lay a solid foundation to improve the medium-range forecasting. The forecasting rangs can be extented longer with NWP products.