Abstract: Development effort at computer aided design of the multivariable control systemhas been intensified for the last two decades.In this paper,a software package named "MCSCAD—SJD"(Multivariable Control System Computer Aidid Design—Shanghai Jiao Tong University)is presented in detail.The package is versatile,expandable,simplein structure and easy to use.Working principles and theoretical background areexplained.The discussion in this paper centers around the system's analysis and synthesisin terms of the YOKOYAMA canonical form.This makes easier the conversion amongthe three different representatons of the system,giving design criteria for distur-bance rejection,pole assigment,and quadratic optimization etc through state feedback.Besides,the paper provides a set of algorithms and programs for polynomical matrixoperation.This package is written in BASIC and first run on Wang-2200 MVP.And preliminary results are obtained.