The development of informatization brings great opportunities for the construction of informatization in hospitals. Hospitals are increasingly dependent on information systems. However, in the process of implementing the hospital information system, user resistance has become an important factor hindering the successful implementation of the system. The existing researches on the causes of user resistance mostly stay in the pre-implementation stage before the introduction of the system. However, the pre-implementation stage does not involve the resistance caused by users' real contact with the system, so the research conclusions are limited. Based on the existing three-factor resistance theory, choosing the resistance in the postimplementation stage of a hospital information system as case study object, starting from the three theoretical perspectives, this paper makes a comprehensive analysis of the reasons for the resistance behavior in the post-implementation stage of the information system, and puts forward that the reasons for the resistance behavior are caused by user motivation, system development technology, network infrastructure, organizational support, organizational management, and other comprehensive caused by multiple factors. Through this study, the conclusions of the existing information system resistance factors research field are further expanded and improved, making the conclusions more comprehensive and specific. This paper not only provides theoretical reference for researchers in related fields, but also provides substantive suggestions for the smooth implementation of information system in hospitals, promotes the transformation of hospital informatization, and improves the level of medical service and social health.