Abstract The working mode of constant-pressure radial piston pump includes mode of constant flow and constant pressure. The dynamic model was established and analysis was made on displacement vibration in frequency domain to the two modes. Measurement mechanism was designed to test the vibration of stator of JB32H-type radial piston pump. It is concluded from analysis and test results that the displacement of stator vibrates periodically on the two modes. The frequency band is narrower on the mode of constant pressure than that on the mode of constant flow because of action of constant pressure control system. The amplitude on the mode of constant flow is smaller than the one on the mode of constant pressure in the range of the frequency band of the mode of constant pressure. The conclusions will be helpful to the noise and vibration control of piston pump.