Abstract: The aim of this paper is to investigate how the suboptimal design of high order control systems can be achieved by the reduced model.A novel engineering design method—Reduced second-order system suboptimal design method is proposed.This method can be separated into three steps:1.using the higher accuracy reduced method to simplify the transfer function of the high order systems,reducing to second-order(or third-order);2.making use of second-order systems optimal design method to satisfy the given requirements of design(percent overshcot,overshoot point time or settling time,stead-state errors);3.ultilizing one dimensional search method and continuous systems digital simulation program(in FORTRAN programming language)to modify the pseudo-damping factor ζ at the terminal of computer,to find the optimal one ζ_opt,and to modify the errors produced by the reduced model.Thus,the compensation networks are determined.Several numerical examples are presented.Certain results obtained by this novel method are studied and compared with the existing achivements.