Drawing upon an overview of more than thirty countries worldwide that have legalized same-sex marriage, this paper explores the primary methods employed for its legalization, namely parliamentary legislation, constitutional review, and referendums. These three methods can be categorized as follows: the legislative model (e.g., Netherlands, Germany, France, Canada, New Zealand), the judicial model (e.g., United States, Brazil, Taiwan), and the referendum model (e.g., Ireland). The paper posits that under different constitutional systems and electoral systems, the primary approaches to the implementation of same-sex marriage may vary. Excluding the rare referendum model, the paper hypothesizes that, among the two main models for the legalization of same-sex marriage-legislative model and judicial model-countries with a parliamentary system and a semi-presidential system with a parliamentary bias tend to adopt the legislative model, especially when the parliamentary electoral system is proportional representation. Conversely, countries with a presidential system and a semi-presidential system with a presidential bias are inclined towards the judicial model, particularly when the parliamentary electoral system is a single-member plurality system, and the presidential electoral system is a plurality system. In summary, by arguing that constitutional systems and electoral systems influence the patterns of same-sex marriage legalization, the paper systematically examines all countries worldwide (including Taiwan) that have implemented same-sex marriage. It explores whether a correlation exists between these institutional factors and the models of same-sex marriage legalization and seeks to validate whether the implementation patterns of same-sex marriage align with the paper's hypotheses on a global scale. [ABSTRACT FROM AUTHOR]