The Anglo-Japanese Alliance in the early 1900's was an expedient measure for hegemony in the Far East.Interests and geopolitics made a great power allied with a weak power.If the two countries' strength changed, the contradiction and the race between them would happen.From this point, we can see that the fundamental reason of the disintegration of the Anglo-Japanese Alliance was that the contradiction and conflict between British and Japanese national interests couldn't be conciliated any more in the range of Alliance.This dissertation analyzes the fundamental reason of the disintegration of the Anglo-Japanese Alliance and its influences on two countries.