Abstract: After the Cold War, the development cooperation between China and Japan in the Mekong River Basin can be divided into three phases, namely, Phase 1.0 (basic cooperation) starting in 1992, Phase 2.0 (mature cooperation) starting in 2013, and Phase 3.0 (new breakthrough cooperation)starting in 2019. From the perspective of development and the development theory, this study aims to explore how China and Japan carry out development cooperation in the Mekong River Basin, why there are different cooperation emphases in various development phrases, and what is implied by the continuous improvement of these cooperation emphases through comparing the different modes of cooperation in terms of mechanism, foreign aid, and soft power. This will facilitate a clear understanding of the process of change in the development cooperation between China and Japan in the Mekong River Basin from Phrase 1.0 to Phrase 3.0, in order to shed some light on the development cooperation projects of the international community.

Key words: development cooperation, mechanism, foreign aid, hard power, soft power