Investor-state dispute settlement mechanism has long faced legitimacy questions including inconsistent decisions and ignorance of host country sovereignty. In order to solve these problems, the European Union proposes the judicial reform of the investor-state dispute settlement mechanism and establishes an international investment court system. The system includes an appellate mechanism which clearly stipulates the host country's regulatory powers and sets high standards of judges’code of conduct. This paper studies and analyzes the appeallte mechanism in the EU investment court system and believes that there are deficiencies in unclear boundary between appeallate scope and the scope of remanding for retrial, unclear selection method of appeallate court members, low salary of judeges, and uneven pratical experience. This paper points out that during the negotiation between China-EU on bilateral investment, the EU-led investment court system can be partially used to establish an appellate mechanism which includes the consultation mechanism. At the same time, the autonomy of parties in dispute should be retained in choosing the members of appellate body and a two-tiered compensation mechanism should be used to ensure the introduction of high-level judges.