The Energy Charter Treaty (ECT) is the only legally binding multilateral agreement in the energy field, which is conducive to promoting energy cooperation. However, since its signing, investment protection clauses such as fair and equitable treatment (FET) have never been revised. Compared with the new standards of the international investment system, they no longer meet actual needs. The issue of FET is extremely controversial in energy investment. Among the existing ECT investment arbitration cases, most are due to the host country’s alleged violation of the ECT’s FET clause, which become the main basis for energy investors to initiate arbitration. In practice, investment arbitration tribunals have made different interpretations of the connotation of ECT’s FET from different angles and levels, leading to application difficulties. As an advocate and main contracting party of ECT, the European Union also pays close attention to the modernization agenda of ECT. The European Union issusd a proposal for the modernization of the ECT, and reformed and upgraded FET clause. China is one of the observer countries of the International Energy Charter, and the modernization of ECT’s FET clause also has important reference value for China. In the context of modernization, combined with ECT’s FET international investment arbitration cases, the interpretation and evaluation of FET clause in the EU text proposal for the modernization of the ECT can give the Chinese government some enlightenment for energy investment protection.