The paper discusses the features and system functions of OPAC& the subsystems of library automated systems, from the aspects of evaluation criteria and user interface design. Some suggestions for designing and developing OPACs are also covered. 本文从OPAC的评价依据和用户界面两个方面论述了图书馆自动化系统中的OPAC子系统应具备的功能与特点,为该子系统的设计和开发提出参考意见。