The executing mechanism of international investment arbitration awards is the important security for operation of investment dispute settlement procedure, whereas application of state immunity is an unavoidable major obstacle to execution of investment arbitration awards. In practice, the execution of investment arbitration awards is faced with surface conflict and awkward issue between effect of arbitral award and plea of state immunity, which refers to application relation of the convention principles and municipal laws as well as choice of application to absolute immunity or restrictive immunity with its judgment standard. So far as application of state immunity principle concerned, this article makes analysis of the feature and difference for dealing with execution of awards under mechanisms of both ICSID Convention and New York Convention with two aspects of ICSID arbitration and non-ICSID arbitration respectively, combining actual cases in investment arbitration for illustration. The substance of this article is to find out and reveal the forming and feasible principle and route in the practice of investment arbitration awards execution. this article points out that the theory of restrictive immunity does not change general principle of enjoying immunity for the state and its assets, but makes the state not enjoy the right of protection for immunity under specific circumstance called exception of immunity which actually determines the scope and degree of state immunity. In concerned with law application for awards execution, the article takes the position that although New York Convention requires its member states should recognize the binding force of arbitral awards, the prevailing parties in practice are still faced with legal barriers, and the law application in the execution of arbitral awards mainly refers to two aspects of state immunity and judicial review.