Japan is one of the major contributors of official development assistance（ODA）and the real leader of Asian Development Bank（ADB）. For over fifty years，Japan has already established a mature ODA-ADB framework. Both as a donor in the bilateral aid system and leader in the multilateral bank system，Japan is pursuing benefits and strategies. Based on Japan’s action of providing aids in South Asia recently，it is discovered that both the ODA and ADB ways of aid contribution conducted by Japan follow the same ideology，showing Japan’s intention of expanding its political and economic influence in the region.