Abstract：At the beginning of the 1960s, there were two regional cooperative organizations the Association of Southeast Asia (ASA) and Maphilindo founded in Southeast Asia. It marked the emergence of regionalism in Southeast Asia. But the regionalism in Southeast Asia came to a premature end before long because of the disintegration of ASA and Maphilindo. The thesis approaches the reasons of the disintegration of ASA and Maphilindo in the deepgoing way from four aspects as national security, ideology, economic benefit and leader's behaviour, thus concludes the factors that restricted the development of regionalism in Southeast Asia.
