In multi-user collaborative interaction systems, the interface serves not only as a medium for human–computer interaction but also as a crucial channel for communication between users. Consequently, the quality of collaborative interface design directly impacts the overall effectiveness of the system. In collaborative systems, different users typically assume distinct roles, and task flows are typically more complex. Compared to single-user interfaces, multi-user collaborative interfaces must account for a broader range of collaboration requirements and characteristics. Although a substantial body of theoretical and practical research on user interface design exists, design methods specifically for multi-user collaborative interaction interfaces are still lacking. Therefore, this study builds on the existing theories and case studies of collaborative systems, extending user-centered design methods. The study emphasizes the analysis of task flows and role relationships in multi-user collaboration and integrates collaboration needs and characteristics throughout every stage of the interface design process. Ultimately, we propose a methodological framework for interface design tailored to multi-user collaborative interaction systems, aiming to provide theoretical support for the development of more advanced and comprehensive collaborative systems.