Fair use doctrine is easily controversial and difficult to judge, and owning to the coming of the new age, fair use doctrine becomes more troublesome. This paper will hold the balance between the right of reproduction of library and the publisher interests by approaching a case under these four elements:the requirement for the Purpose and character of the use; The nature of the copyrighted work; The amount and substantiality of the works used in relation to the copy?righted work as a whole;The effect of the use upon the potential market for and value of the copyrighted work.