Axial piston pump is fluidsolid coupling mechanical equipment. Its vibration characteristic is complicated when working. This paper uses the characteristic linefast Fourier transform method (MOC  FFT) in the plunger pump to study vibration characteristics caused by fluidsolid coupling. Using the MOC to solve the fluidsolid interaction’s (FSI) partial differential equations (1), then the vibration characteristics of pipeline system in time domain can be achieved. Using the fast Fourier transform method, the natural frequencies of the piping system can be obtained. It has the advantage of characteristic line method for the coupling vibration model is clear, easy to calculate; And using the method of fast Fourier transform the vibration characteristics to the frequency domain. According to study the vibration characteristics in the frequency domain, this paper achieved the frequency which the type of A10V pump should be avoided when working and change rules of the angle of swash plate, pressure and the speed of rotation how to affect the intensive frequency vibration spectrum which is caused by the FSI.