On the basis of the introduction of the basic principle and method of teaching design, in the light of the design of "Microcomputer Principle and Interfacing"CAI courseware, this paper discusses the teaching desig n of the coursew are in detail. That includes analysis of learning need, analysis of teaching target s and content s, teaching st rategies, the choice of teaching media, feedback and helping. For every step in the teaching desig n, it all gives the concrete pract icable methods. Using the principle of teaching design to guide CAI coursew are design is CAI coursew are necessary scient if ic t rend.