Abstract: User Interface(UI) plays an important role in computer systems,whose quality is guaranteed by user interface evaluation.There have accumulated a lot of evaluation guidelines from former experiments,but few have been utilized by UI designer.Here we apply expert system technology to construct a UI evaluation knowledge base and to give a UI evaluation system UIEV -Pro,which can evaluate user designed interface and give them improving suggestions.This system combines UI evaluation with UI design and gives UI designer a comprehensive platform to improve the quality and efficiency of user interface design.