The gain of the Static Var Compensator (SVC) voltage regulator affects its response speed and stability. According to the detailed investigation on the application background and technical route of the transmission system SVC, this paper mainly researches the influence on the SVC voltage regulator due to the changes of complex transmission system, analyzes and summarizes the gain control method of SVC voltage regulator used in transmission system, and puts forward a kind of adaptive gain control method based on integral closed loop control. The gain adaptive control can adjust the gain of the voltage regulator properly when the system operation mode is changed or the voltage regulator output continues to surge. The method is proved to be correct through the RTDS simulation. The method has the following advantages:convenient to realize, fast inhibitory oscillation, gain optimizer to improve the dynamic response characteristics and wide range of application.