An integration method was used for ICP vibration accelerome ter signals measured in engineering. By using the method, more precise vibration signals of speeds and displacements are obtained and then the phase space analysis using vibration signals is realized, and the nonlinear time-domain operating features of complex mechanical structures are identified. In order to understand the operating features in nonlinear frequency domain of complex mech ani cal structures, a frequency domain analysis method is proposed based on neural n etwork identification model. The above mentioned methods are applied to analys is of nonlinear operating feature of large vibrating screens.