Abstract: The principle of party autonomy in international investment arbitration originates from international commercial arbitration, but party autonomy is expressed differently in the two types of arbitration. International investment treaties not only directly reflect the party autonomy of the host countries but also indirectly reflect the intentions of investors. Additionally, from the consent required for establishing jurisdiction in international investment arbitration to the procedural rules during the arbitration process, one can see the emphasis placed on party autonomy within the arbitration procedure and the balance of party autonomy between the host countries and investors. However, in practice, there are often situations in international investment arbitration where arbitral tribunals expand their jurisdiction, apply the law incorrectly, or ignore the procedural rights of parties, demonstrating a lack of respect for party autonomy. In international investment arbitration, it is important to respect and balance the parties’ autonomy, while appropriately limiting it in consideration of public interest. Respect for party autonomy by arbitral tribunals can be overseen through mechanisms such as amicus curiae submissions and appellate bodies. Furthermore, the autonomy of both the host countries and investors can be balanced and limited through means such as joint interpretations by treaty states and requiring tribunals to adhere to reasonable interpretative methods.