The Static Var Generator (SVG) plays a significant role in the dynamic characteristics of power systems after large disturbances. The accuracy of the SVG controller parameters is the key to transient simulation of power systems with power electronic equipment. This paper presents a parameter identification method for an SVG controller based on RTDS hardware-in-the-loop test. This method establishes the SVG controller-RTDS hardware-in-the-loop test system to obtain the SVG response data as the measured data. For different combinations of controller parameters, BPA software is used for transient simulation, and parameter identification is based on the Least Squares (LS) index of transient simulation results and measured results. The correctness and effectiveness of the proposed method are verified by the hardware-in-the-loop test of an actual SVG controller, which can better meet the application requirements of the actual power system transient simulation. This work is supported by Science and Technology Project of Zhejiang Province (No. 2019C01149) “Key Technologies Research and Application of Intelligent Regulation and Control of Distributed Network Oriented to Integrated Energy Interconnection” and Science and Technology Project of State Grid Zhejiang Electric Power Co., Ltd. (No. 5211DS180031).