To study the dynamic issue of a tiltrotor aircraft, an analytical method was established for the tiltrotor-fuselage coupled model. Based on the generalized Kalman filter method and optimal control theory, the application study of the higher harmonic control(HHC) in the vibration reduction of a tiltrotor was conducted, the control process and control strategy were constructed. Taking XV-15 as an example, the closed-loop vibration control on a tiltrotor was simulated through HHC method. The results show that 3Ω hub loads were significantly reduced with a transfer matrix on-line identification, the maximum and minimum reduction are respectively 90% and 18%.When HHC control was applied to the tiltrotor, the blade lift of the outboard section showed a significant change with rotor azimuth. It can indicate that the vibration control effect mainly comes from the reduction of the high-frequency aerodynamic force.