The Asia-Europe Meeting (ASEM) is regarded as an important international institutional arrangement form in today's world. At present, there are many conflicting opinions on the performance of ASEM which are stirred up by its institutionalization. This thesis aims to explore the issue of the institutionalization of ASEM, covering such issues as the origin and role of ASEM and the challenge and prospect facing it. In this thesis, a modified model on the basis of Tian's model on international institutional choice derived from transaction cost economics is applied to analyze the variables having a great impact on the degree of institutionalization. This is a rational-design analysis mainly based on the approach of rational choice institutionalism. The different theoretical perspectives offered by International Relations (IR) theory are imperative to study ASEM's institutionalization in this analytical process. This thesis adopts a qualitative research method. At the empirical level, the degree of institutionalization of ASEM is identified. At the theoretical level, this thesis contributes a case study to the rational design of international institutions in a new angle different form classical game theory. In terms of the model, it is the first time the element of regional actors, in addition to the state actors, is brought into this analytical framework. As a by-product, interregionalism as a new research approach in IR is further elaborated based on this case study.