Abstract: According to the changes of user demand in the "Internet + Library" environment, this paper pointed out the development direction of library business re-engineering, including the standardization of service platform, the datamation of business processing, O2O, integration of smart service, and proposed the contents of "Internet + Library" business re-engineering from the aspects of re-engineering service model, reconstructing organizational structure, reorganizing business process and optimizing business space, so as to promote the development and reform of library business.