This paper firstly defines the civil legal relationship between readers and the libraries, to research book borrowing reservations on network from civil law perspective. Then it analyzes the theories of offer, commitment, establishment of contract and others that apply to readers who reserve books borrowing and libraries which provide books reservation services. Readers' misuse of book reservating right can be dealt with according to contracting fault liability. It also damages other readers' right to gain information. Libraries can make new offer for readers, and cancel illegal readers' reserving rights of borrowing books, to prevent this kind of behaviors.