Abstract: Communication is an interactive system, involving different fields and different links, with different subjects. From the point of communication subjects, communication freedom in International Law refers to communication freedom of nations, international organizations and citizens, which are protected and restricted by respective international legal systems. From the point of communication fields, communication freedom can be divided into freedom in private fields and public fields. The former ought to be protected heavily by international law and the latter should be subjected to severe restrictions. From the point of communication links, communication freedom in international law is a right system comprising right to know and right of expression. During the protection and restriction of communication freedom, we should not only avoid conflicts of communication freedom and other rights else, but also put emphasis on harmonizing two sorts of rights in communication freedom. The current international law has established basic framework of protection and restriction of communication freedom. However, it is faced with many challenges presented by the network communication era, and needs urgent further improvement.