45 years ago, on 8/8/1967 in Bangkok, the ASEAN came into being marking an important historic landmark, opening a new stage of cooperation among Southeast Asian countries, the foundation for the building of the present ASEAN. Since its foundation, ASEAN has given priority to promote economic growth, social progress, cultural development, enhance cooperation and mutual assistance among the member countries as well as promote peace, stability in the region. This essay reviews the ASEAN's 45 years development, its outstanding achievements in the regional cooperation and integration. The essay also refers to Vietnam's major contributions to the developments of ASEAN.