Abstract: The MFN clause has become one of the core provisions of an international investment treaty and plays a very important role in the liberalization of international investment. The“host country - investor”dispute settlement procedure is laid down in a large number of modern international investment treaties.This procedure，however，has different contents in different investment treaties，of which the host country and the investors are wild apart in their understanding，causing a controversy over whether the MFN clause can be applied to international investment dispute settlement. According to the theory of the international treaty law，the purpose of the MFN clause in international investment treaties is to promote，rather than deplete，the contracting parties’interests. From the perspective of the investors’home country，the expanded application of the MFN clause in international arbitration practice to the international investment dispute settlement procedure is more disadvantageous. This will seriously affect the investor’s home country’s understanding and reasonable judgment of the legal obligations in the treaties，which may even be contrary to the treaties’original intensions. Thus，the application of the MFN clause should not be included in the investment dispute settlement procedure unless the contracting parties specify such an application in the treaties.

Key words: international law, MFN clause, investment dispute settlement, investor’s home country, international arbitration