Abstract: he concept and basic requirements of computer aided design,the characters and requirements of computer aided aircraft conceptual design system are described The first thing in developing a design system is to create the models.Design object model and design process model according to the design theory are established. The design object model is applied to integrating all design tools,and the design process model is applied to describing design process and design activities.The correctness and effectiveness of the established model have been testified through the development of aircraft conceptual parameter selection system.

Key words: computer aided designs, aircraft design, models