Abstract: Arbitrators undoubtedly have a duty to apply antitrust law, and are expected to do so by the intention of the parties, the legal demanding of relevant private international law and the requirement of sustainable development of international commercial community. The duty of arbitrator to apply antitrust law can extend to the application of antitrust law even ex officio, provided the basic principles of international commercial arbitration, such as the party autonomy, due process and right to be heard and be treated equally, have been faithfully respected.