Based on the method of PolyMAX

a system of modal analysis is built

the model of JZQ-250 gear-box is set up under the LMS modal analysis module.The relating modal datum are obtained by hammering test of single-input multi-output analysis method

then the transfer function is established after the analysis of modal datum.The various modal parameters of the gearbox are obtained by order selection and fitting of the datum which extracted through the method of PolyMAX Modal Parameter Identification.Through the comparison with calculating modal

the validity and reliability are proved.The theoritical basis for the improvement of the gear box structure characteristics and the fault diagnosis of gearbox are provided.The natural frequency is extracted from the modal analysis

the wavelet decomposition of the corresponding frequency band component is removed

and the noise reduction processing on the fault signal is achieved.