An active control method of trailing edge flap is investigated for suppressing high frequency vibration of wind turbine blades. The structure is modeled as composite blade beam with circumferentially asymmetric stiffness (CAS) configuration, which is based on the analysis of the elastic flap-wise/twist displacements and incorporates the angle control of trailing-edge flap driven by a stepping motor. Aerodynamic expressions of the aeroelastic system are based on a novel quasi-steady model suitable for trailing-edge flap. The partial differential aeroelastic equations of the aeroelastic system are solved based on the discretization function of Galerkin method. The high-frequency vibration of the blade is successfully suppressed by the active control based on the swing angle of the trailing-edge flap. The active control is realized by H∞ algorithm using linear matrix inequality (LMI) design and state observer design. Time-domain stability analysis and robust control method is investigated to realize displacement response analysis and robust performance analysis, and input signal display of trailing-edge flap angle. The optimization is investigated to mechanism of LMI is to optimize uncertain robust performance parameters based on the selection of robust control parameters, so that the controlled displacement and control input are kept within reasonable ranges. In order to reduce the influence of state variable detection error in full state feedback, state reconstruction and state observer are used to improve the control performance. At the same time, the reliability and robustness of H∞ control algorithm based on LMI are verified by comparisons of the results of high-frequency vibration control using different robust performance parameters and different wind speeds. Based on a real-time OPC technology of S7–300 PLC and WinCC configuration software, a process control experiment is adopted to verify the feasibility of the control algorithm in the engineering application. A real-time engineering application feasibility scheme is provided for the control method that cannot be conventionally implemented in the controller hardware due to the complexity of the intelligent control algorithm.