In this paper, the frictional vibration behavior under different wear states was investigated by the friction and wear experiments of the piston ring against the cylinder liner of marine diesel engine on CFT-I tester. The time-frequency features of frictional vibration were analyzed by harmonic wavelet packet transform (HWPT) and the variation of frictional vibration from running-in wear to steady wear and violent wear states was studied by defining characteristics parameter K using singular value decomposition (SVD). The result shows that the time-frequency features of frictional vibration vary with the wear time and can reflect the wear states of tribological pairs. The variation of characteristic parameter K of the frictional vibration is accordingly consistent with that of the friction coefficient and indicates that the wear progress of the tribological pair goes through various stages, namely, running-in wear, steady wear, and violent wear. Therefore, the frictional vibration can be used to predict the wear process and identify the wear states of tribological pairs.