A monitoring and control system of sub synchronous oscillation is composed of three parts:the monitoring and control device, the synchronous Phasor Measurement Unit (PMU) and the monitoring and analysis main station. The detection and control device identifies sub synchronous oscillation conditions quickly and accurately through the power tracking trajectory identification technique, meanwhile combining with the modal frequency characteristics of thermal power unit, and using the control strategy of the wheel grading, quells the sub synchronous oscillation of power grid quickly before thermal power unit torsional vibration protection action. The SSO panoramic analysis scheme is proposed. By calling continuous recording file of PMU, it achieves automatic calculation of the whole network sub synchronous oscillation state and visual display in the monitoring and analysis master station, which creates favorable conditions for the research of sub synchronous oscillation mechanism. At last, the feasibility and effectiveness of the system are verified by the case of engineering application. This work is supported by Science and Technology Project of State Grid Corporation of China (No. SGTYHT/14-JS-188).