The transient exciting test is one of the important methods to get the dynamic parameters of mechanical systems. Adopting the transient exciting methods，the dynamic exciting test has been carvied out for the main spindle system of machine tool Sl-235 with super-accuracy in this paper. The test technique the foundamental principle and the characteristic of signal processing of the transient exciting methods are presented here Final1y the natural friqnences，the damping ratio and the dynamic stiffness have been determined. The transfer function of system has been obtained by Levy's direct curve fitting methods.