This paper presented a new H∞ controller design approach. It has following characteristics: it models the harmonic disturbance and connects it with the system model to form a linear parameter-varying system with the harmonic disturbance frequency as varying parameter. Aiming at the characteristic of the system, it uses a single quadratic Lyapunov function based method to design linear parameter-varying gain-scheduled H∞ controller, which guarantees the realization and performance of the controller. Since the parameters of the designed controller can schedule with the frequency variation of the harmonic disturbance and satisfy some performance specification requirements, it can effectively reject all known varying frequency harmonic disturbances. Compared with the interpolation based gain-scheduling approach, this approach is simple in structure that is easy to be realized and can guarantee the global stability. Its effectiveness is verified by the numerical simulation and the comparison results with an LQG and a generalized H∞ controller.