G20 gradually attracts more attention from the world after two financial crisis. While, along with the deepened globalization, the interdependence becomes more significant and beneficial. Hence, the international institutions as platforms become valuable, in which nations could share information, communicate and negotiate, etc. Especially, G20 is a new try for international society, providing a relative fair chance for developing countries to participate global affairs. Although there are many debates on G20’s position, the finical crisis has proved its value. The theoretical basis of this study about G20 is neoliberal institutionlist. And this study will be done especially from the perspective of institutions and cooperation. The thesis will exert the model of rational design to study G20’s characteristics and analyze why it has these characteristics, how these characteristics are formed and processed. By means of analysis, we could have more deep understanding on the existence and necessity of G20. Although G20 is not prefect, it is necessary to exist under the background of global governance. The researcher hopes to shed some lights on the the future study of the G20 in global governance