The good quality of Senayan Library Management System (SLiMS) according to its users is one of the determining factors for success in implementing library services to users. SLIMS can be a means of providing information and communication for its users. This study aims to measure the quality of the SLiMS service that can be provided to its users by using the webqual 4.0 method. The webqual 4.0 method has 3 (three) dimensions used to describe the quality of SLiMS services, namely usability quality, information quality, and service interaction quality, then mapped in the form of the Importance Performance Analysis quadrant (IPA). The results of this study indicate that the overall index of the quality of SLiMS service users is 83.2%, which means that the quality and performance of the service is very satisfactory. Based on the IPA quadrant, the research results show that 4 statement items in quadrant A, namely the SLiMS website is easy to operate, the interaction is clear and understandable, has a good reputation, and is safe from viruses, then there are 5 statement items in quadrant B, namely the SLiMS website is easily accessible, has a visual attractive, presenting up to date information, making it easy to communicate with the UPT Library, and guaranteeing a high level of trust, quadrant C there are 5 statement items, namely having easy navigation, information presented in an appropriate format, submission of personal data is kept confidential, providing space for personalization and community, in quadrant D there are 6 statement items, namely the preparation of the right information layout, having complete facilities, providing clear and detailed information, providing reliable and accurate data information, and providing relevant information