An objective of this study is to develop a new method for the prediction and the avoidance of chatter vibration in milling operation of thin-walled structure by using 3D-CAD and CAE approach. Also, a new identification method for the modal parameters of a vibration system by analyzing radiated sound pressure from vibrated workpiece accelerated by an impulse force is proposed. Then chatter stability lobes are predicted using those modal parameters. Stiffness and modal shapes of the workpiece were obtained using commercial finite element method (FEM) code, and the model was made by 3D-CAD. The damping ratio, which cannot be determined through FEM analysis, was identified from the relationship between the sound pressure radiated from the workpiece and the impulse force. Chatter stability limit was analyzed with the modal parameters obtained through these procedures, and compared with the cutting experiment on the chatter stability limit. The experimental and predicted stability limits are in good agreement. The proposed procedure will help to set the cutting conditions to avoid the chatter.