The strong aerodynamic interference exists between the upper and lower rotors of a coaxial high speed helicopter, which has a significantly influence on the aerodynamic characteristics of the rotors. Based on the feature and considering the efficiency of the aeroelastic coupling calculation, the initial induced velocity distribution calculated by rigid-wake model, together with the wake geometry feature of a single rotor calculated by free-wake model, are the initial iteration values for the prescribed-wake model of a coaxial helicopter. The main calculation modules:The blade fully intrinsic dynamic equations of the coaxial twin rotors, the constraint equations between the blade and the bearings and the aerodynamic models, including the wake models and Leishman-Beddoes unsteady dynamic stall model and Pitt-Peters dynamic inflow model, are the basis for establishing a computational model of the coaxial twin rotors vibration load considering the aerodynamic interference and coupling iteration between the upper and lower rotor. The forces and moments on the sample XH-59A, which is the certification machine of Sikorsky, are calculated with the help of the model. The computational results are in good coincidence with those from the wind tunnel test.