Abstract: In order to obtain the characteristic messages of condition monitoring and fault diagnosis of hydraulic pump, short-time Fourier transform method was used to process non-stationary signals for the hydraulic pump vibration power spectrum, and a computer fault diagnosis testing system was set up. An axial piston pump fault diagnosis is used as an example to illustrate that vibration analysis is an effective way for condition monitoring and fault diagnosis of hydraulic pump and that can be applicable on the spot.