When Foreign states waiver the privilege of jurisdiction immunity, the domestic courts hereby obtain the jurisdiction over the foreign states. However, it is difficult for the courts to determine the modality of waiver, and the key components of express waiver and implied waiver. In this field, the judges of American Courts estimate whether foreign sovereignty' behavior constitute express waiver or implied waiver through discretion and strictly narrow interpretation, on the basis of Foreign Sovereign Immunity Act 1976 and Congress Report of 1976, in order to balance interests of private parties against the sovereignty. To our own foreign sovereign immunity legislation in the future, not only do it learn from American advanced experience, but also do it in line with our fundamental realities, and adopt enumeration method, for making it easy to operate and maintain the consistency of the judgments.