Recently, with the gradual separation of international investment arbitration from the international commercial arbitration system, the code of conduct for investment arbitrators is undergoing the transition from“the integration of commercial and investment”to“the separation of commercial and investment”. The differences in procedure and in substance between investment arbitration and commercial arbitration put forward more explicit, specific, strict, and self-contained requirements for the code of conduct for investment arbitrators, which conforms to the expectations of both investors and host countries for international investment arbitration mechanism. On the one hand, the establishment of a uniform code of conduct for investment arbitrators can make up for the deficiency of international legislation in investment arbitration ethics, making it more systematic to regulate and restrain investment arbitrators. On the other hand, the professionalization of investment arbitrators is a significant breakthrough in the current ISDS regime. In short, the development of the code of conduct for investment arbitrators can effectively fill the gap in the current field of investment arbitration and improve the legal system for international investment.