In case of uniformly distributed damping, the system can be expressed as real mode shapes and therefore the prediction of structural modification can be achieved with high accuracy. However in case of un-uniformly distributed damping, such as automobile suspension consisted of link, bush, the system should be expressed as complex mode shape, resulting less accurate prediction. In this paper, a numerical model is used to reveal the cause of such inaccuracy and then new algorithms are proposed to improve such inaccuracy. Finally by using proposed algorithm, an accurate vibration model of actual automobile suspension is obtained to be able to predict the change of vibration after structural modification.