This paper is to research on the role of party autonomy in the decision of applicable law for the arbitral proceeding, arbitral award and arbitration agreement, in the decision of the place of arbitration, in the composition of arbitration tribunal, and the choice of arbitral proceedings. The principle of party autonomy is fundamental to arbitration in general and to international arbitration in particular. Generally the tenn of party autonomy is used as the autonomy of the parties to decide all aspects of an arbitration procedure subject only to certain limitations of mandatory law. Party autonomy permits the parties to a commercial arbitration to choose the laws and make the rules which govern the arbitral proceedings. Party autonomy allows the parties freedom to choose the applicable laws for the arbitral proceeding and the place of arbitration. Party autonomy is recognized in relation to the choice of law for the merits of the dispute as well as for the arbitration agreement and the arbitration procedure. On the basis of the recognition of party autonomy in international treaties, national legislation and court decisions, arbitral practice has generally accepted and enforced party autonomy both regarding the procedure and the applicable substantive law. All modern institutional rules of arbitration follow that line. Today it is recognized by national legislators all over the world to the effect that the jurisdiction of national courts can be excluded by arbitration agreement and that the parties may choose the law applicable to arbitral proceedings. Limits on party autonomy are imposed by mandatory provisions of international or national law or of institutional arbitration rules regarding the procedure. Mandatory laws at the place of the arbitration or under any procedural law chosen by the parties may restrict party autonomy. These mandatory laws usually take the form of public policy considerations in the arbitration. Limitations on party autonomy have been reduced more and more, and the trend of modern national as well as international legislation on arbitration leans clearly in the direction of a maximum of party autonomy.