In order to improve the stability and flexibility of the static synchronous series compensator (SSSC), at the same time considering the energy storage capacitor voltage in DC side of SSSC dynamic adjustment process and the interaction between the state variable, this paper establishes a SSSC five order dynamic mathematical model for affine nonlinear systems with uncertain disturbance parameters. On the basis of robust H∞ control method, the method of SDM feedback linearization H∞ is used to design the nonlinear robust controller of the system. In view of the design process of Riccati equation, MATLAB robust control toolbox is used to obtain the specific control parameters of the controller. Using the MATLAB modeling and simulation of the system, with traditional nonlinear optimal control system simulation results contrast, this paper verifies the controller’s effectiveness and superiority on improving the stability of the power system.