Series compensation of transmission lines is essential for power systems transfer capability enhancement, reactive power equipment and steady-state voltage stability in power systems. However, it leads to increase the risk of sub-synchronous resonance. Sub-synchronous resonance is one of the most critical issue to power system stability which can be described as general oscillation problem at one or more frequency below synchronous frequency. Frequency scanning technique, eigenvalue analysis technique and electromagnetic transient analysis technique are frequently used in the literature for the purpose of analysis sub synchronous resonance in power systems. In this paper, Using IEEE first benchmark model (FBM), the susceptibility of the system to the SSR is investigated by the eigenvalue technique and electromagnetic transient analysis technique. PSCAD/EMTDC tools is used for electromagnetic transient analysis technique. Furthermore, the susceptibilities of the system are compared for different compensation levels in this study.