Interlibrary loan refers to the borrowing of documents that are not available in our library from other libraries according to the system, agreement, method and charging standard of interlibrary loan when readers need them. On the other hand, when foreign libraries make interlibrary loan requests to our library, they lend the documents owned by our library to meet the literature needs of foreign libraries. Applicable to returned documents and copying unreturned documents. Of course, documents that are copied and not returned can also be obtained through document delivery.

Document delivery is a non-recoverable document providing service, which directly or indirectly delivers the copies of documents needed by users in an effective way and at reasonable cost. It is fast, efficient and simple. Modern document delivery is developed from interlibrary loan with the support of information technology, but it is a better service than interlibrary loan. By carrying out document delivery service, the contradiction between the shortage of library funds and resources and the increasing demand of readers for documents is not only alleviated, but also plays a very good supporting role in teaching and scientific research.