The book number, among various steps of book processing works, needs more careful attention and better-organized knowledge, and it is more sensitive than other parts of cataloging. This paper will give some suggestions on ways of constructing a book number, including the definition and the types of edition indication within a book number, and analyse some problems related to their application into real situation. Three possible ways of edition indication with in a book number were explained, and examples were given for each of them. Problems occurring when these codes were applied to books were analysed. In addition to the generally recognized meaning of the book number as a mean of differentiating similar works, the edition indication can make it possible for both the library staffs and the users to identify the characteristics of a work only with the book number. Searches for mere convenient and effective ways of edition indication might be related to the cost-effectiveness of book processing, and of library operation.