Abstract: Aiming at the multi-variable parameters in the automatic control system,this paper firstly plots the root loci of the sys-tem with two variable parameters by using Matlab,then analyzes the results of the corresponding parameter change on the steady-state performance and the transient performance of the closed-loop system,and finally gives the simulation to prove the validity of theoreti-cal analysis. The root loci drawn in Matlab can improve the students to understand the influence on the performance of the system with varying parameters,and to enhance the effect of teaching in class.