[Purpose/significance] Domestic subject service is mainly based on the active service of librarians and the passive acceptance of users. While achieving certain results, it also exposes the problems of low engagement and weak cooperative sense of users as well as diminished personal accomplishment of librarians, which leads to the unsustainable development of subject service and difficulties of forming a positive long-term mechanism. From the point view of user behavior habits, this study aims to provide reference for university libraries to develop sustained and effective subject services by cultivating users' active triggering behavior of demand pain points, developing dependence on subject service habits, and enhancing users' stickiness and loyalty.[Method/process] Based on the hook model theory and information interaction model, a questionnaire was designed to investigate the behavior habits and needs of users of subject service in acquiring and utilizing academic resources. Then, by investigating the behavior characteristics and rules of different users, the real needs of users were found and located, and a three-stage anchored service strategy framework was constructed.[Result/conclusion] The research shows that the three-stage service strategy follows the hook model theory, circulates and integrates with each other. It can give full play to the advantages of each librarian's specialty and team cooperation, enhance the value of subject service and user loyalty, stimulate users' pain points from the outside which from low to high, and users actively trigger and complete the pain points. Finally, staff precisely locate the pain points of users' needs and provide effective service incentives to induce users to re-invest or upgrade pain points, thus forming a closed-loop discipline services.