Abstract: The theory, method and the results of experiment on identifying the dynamic characteristics of journal bearing with PRBS mechanical exciting signal are described in this paper. With pseudo-random excitation, the transfer function of journal bearing could be obtained directly. Thus eight dynamic coefficients can be estimated. Comparison with other mothed this approach possessesofrapid exciting procedure, small exciting force magnitude and does not any effect for normal operation of machine-set. Consequently, it is suitable for measnuring on line. The PRBS mechanical exciting rig is a new kind of exciter. The main advantages of this exciter are higher exciting energy, reliable operation and low in price. It has been proved that it is more valid for identification of oil-film coefficients and it is a useful technique for dynamic system research.