Users' loyalty to digital libraries is declining. There are quite a few studies on user satisfaction in digital libraries. However, the affinity theory and the loyalty theory are rarely applied to study digital library use.The purpose of this study is to integrate the information system success theory, Technology Acceptance Model, and affinity theory to identify the factors that may affect user satisfaction and user loyalty to digital libraries. A total of 426 valid survey questionnaires were collected. The structural equation modeling was employed to test the proposed research model and hypotheses. The results indicated that, instead of information quality, system and service quality significantly affected perceived ease of use, perceived usefulness and digital libraries (DLs)’ affinity. Both perceived ease of use and DLs' affinity impacted on perceived usefulness. Moreover, perceived usefulness and DLs' affinity had significant effects on user satisfaction, thereby affecting user loyalty. We also found that user differences, including age, gender, and educational level, significantly affected DLs’ affinity, which further influenced user satisfaction and loyalty. Implications for librarians and service providers to improve the quality of digital libraries are provided.