Abstract: The formation, maintenance and decay processes of blocking high over East Asia in summer of 1986 are analysed by kinetic energy equations with various wave-number domains. It is found that the representative wave number of blocking high is wave-number 5 in the case, which is in the long wave domain, not wave-number 2. During the formation and maintenance stages of blocking episodes, the kinetic energy at wave-number 5 increases through the wave-wave nonlinear interaction and decreases through the wave-mean flow interaction. During the maintenance stage, the available poteneial energy at wave-number 5 is transformed into kinetic energy as to maintain the blocking. These physical processes are reversed in the decay stage, but the wave-mean flow interaction leads to the decreasing of westerlies in the high latitude, and maintaining the blocking high.