Abstract: In this paper the history of studying the low frequency variation is reviewed. An analysis and some of synoptic/climatological points of view is put forward on the formation and maitainance of the blocking flow pattern through the diagnoses of obser vation facts com bined with some experiences in forecast practice. It is emphases that the eastward steepening of low troug hs in the upstream of the blocking high, the SST variation and the topography effect are the major factors influencing the variation of the blocking high. The wave-flowint eraction during the maint enance of Woollier Mountain blocking high is studied through the layout of the barocl inic trough (transient wave) and the blocking flow. This will give a primary basis for the further theoretical study on the formation mechanism of the blocking high.