Abstract: Using the method of climatic statistics,the filtering analysis is made for the data of typhoon occuring in the western Pacific(affecting mainland China)during 1949-1992,and their objective criterion of explosive development is determined. On this bases,their space-time distribution and average environment flow field in lower and upper troposphere level are given.The results are as follows.(1) The explosive intensification of typhoon mainly occurs in the Southern China Sea from July to September every year.It is rare in the East China Sea.(2)According to variation of central pressure and maxiam velocity near the centre,the explosive development may be classfied into three patterns.In the lower tropospheric level,the average environment flow field in the third pattern are different from the other.Their explosive development mainly results from the circulation and weather systems in the low latitude.The role of those in middle-high latitude does not have much importance.