An effective method for delaying the dynamic stall of helicopter retreating blade by using the trailing edge flap has been established in this paper.The aerodynamic loads of blade section are calculated by using the Leishman-Beddoes unsteady two-dimensional dynamic stall model and the aerodynamic loads of the trailing edge flap section are calculated by using the Hariharan-Leishman unsteady two-dimensional subsonic model.The analytical model for dynamic stall of elastic blade with the stiff trailing edge flap has been established.Adopting the aeroelastic analytical method and the Galerkin’s method combined with numerical integration,the aeroelastic responses of rotor system in high-speed and high-load forward flight are solved.The mechanism for control of dynamic stall of retreating blade by using trailing edge flap has been presented.The numerical results indicate that the reasonably controlled swing of trailing edge flap can delay the dynamic stall of retreating blade under the same flight conditions. An effective method for delaying the dynamic stall of helicopter retreating blade by using the trailing edge flap has been established in this paper. The aerodynamic loads of blade sections are calculated by using the Leishman-Beddoes unsteady two-dimensional dynamic stall model and the aerodynamic loads of the trailing edge section are calculated by using the Hariharan-Leishman unsteady two-dimensional subsonic model. The analytical model for dynamic stall of elastic blade with the stiff trailing edge flap has been established. Adopting the aeroelastic analytical method and the Galerkin’s method combined with numerical integration, the aeroelastic responses of rotor system in high-speed and high-load forward flight are solved. The mechanism for control of dynamic stall of retreating blade by using trailing edge flap has been presented. These numerical results indicate that the reasonably controlled swing of trailing edge flap can delay the dynamic stall of retreating blade under the same flight conditions.