With the revival of internalized liberalism, the utility demand of state regulation power in the field of international investment is more urgent. The Security Exception Clause attached with the nature of self-judging is undoubtedly a sharp tool to safeguard national interests. The key factor to realize the self-judging function of the clause lies in the determination of its nature and the establishment of review standard. The Investment Dispute Settlement Body should adopt the attitude of“tolerant on input, strict on output”, breaking the limitations of the phrasing structure, taking into account the national attitudes and other factors, identifying laxly the nature of selfjudging,and controlling strictly the review standard, to distinguish the invoking State’s subjective intention and whether its security interests are threatened, the“necessity”of measures is, in principle, at the discretion of the invoking State. However, the Investment Dispute Settlement Body has the power of“good faith review”, with the addition of the review of procedural obligations, in order to avoid the host country to take advantage of the National Security Exception Clause from the nature of the convenience of investment protection.