To study how the linear optimal comprehensive controller of Static Synchronous Series Compensator (SSSC) and excitation to suppress sub-synchronous resonance in the disturbance situations of mechanical and electrical. A classical theory of linear optimal control theory and sub-time optimal control weighting matrix method are proposed. Compared to no controller and the SSSC optimal controller (LOSC), the system eigenvalue parameter analysis shows that LOSEC can improve system damping ratio and operational stability. Finally, the electromagnetic transient model of single machine infinite bus power system including SSSC is established by Matlab/Simulink. The simulation shows that under the short-circuit disturbance, using LOSEC method to suppress sub-synchronous resonance effect is more significant.