Abstract: Advanced Blade Concept （ABC） coaxial helicopter has a large vibration problem. In order to study the vibration mechanism， a ABC rotor/fuselage coupled aeroelastic model is established， in which the blade is modeled by a finite element beam model， the fuselage is a fine finite element model. In order to improve the accuracy of the aeroelastic response analysis， combined with the traditional CFD/CSD coupled analysis method and the free wake， a CFD/CSD/Free Wake coupled method is proposed to solve the wake dissipation problem of the traditional method， and the calculation efficiency is guaranteed. Based on this method，the coupled aeroelastic response analysis method of ABC helicopter is established. Then， the variation rule of the vibration re?sponse of the key position with the forward ratio and the rotor cross angle is summarized， and some significant conclusions are obtained.