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This paper deals with a hybrid linearization method of a power system with FACTS (flexible AC transmission system) devices. The linearized power system model provides useful information, which is necessary for the small signal stability study and the control design. Although the algebraic linearization method provides an accurate and parameterized linear system, it may incur computation burdens for the large power system with multiple FACTS devices. The numerical identification of linearized system by utilizing input-output numerical data is highly versatile. However, quite an amount of valuable information may not be fully utilized. In this paper, a hybrid method in which the algebraic and the numerical linearization technique are combined is presented. While both the power system and the FACTS devices are separately linearized by using algebraic method, the interaction terms between the power system and FACTS devices are numerically identified by adopting the quadratic optimization technique. The proposed hybrid linearization technique is tested on the WSCC system in which one TCSC (thyristor-controlled series capacitor) is installed. Both eigenvalue analysis and time-domain simulation results verify that the proposed method can effectively identify the linearized model of the power system with FACTS devices.