Some ICSID tribunals try to expand their jurisdiction over investor-state disputes on investment in practice. The author tries to review, figure out and categorize the various approaches commonly employed by tribunals to expand the jurisdiction. More importantly, the author tries to dig into the possible reasons behind the practice and the potential damages caused therefrom. The conclusion is that the expansion of jurisdiction adds to the legitimacy crisis of international investment arbitration over investor-state dispute and thus it is necessary to create a proper mechanism to limit the tribunals' discretion to expand jurisdiction.Chen Huiping