The purpose of this research is to develop a library system by implementing integrated procurement flow, return and borrowing book, so that the inter-library loan can be done in an integrated manner, with the hope to facilitate members to borrow varied books thereby increasing library transactions. The methods used include the method of analysis in the form of literature and field studies to observe the activities of the running system, interviews with stakeholders, user surveys and design method using the Unified Modeling Language, and design the system architecture and features. The result of this research is the development of the library system by implementing an integrated flow of circulation of books between libraries. The conclusions of this research is to implement an integrated book circulation between libraries, then the inter-library loan can be done in an integrated manner.