Abstract: To analyze the startup and operation stability problems of high pressure multistage centrifugal pump water lubricated bearing - rotor system, analysis and judgment about the dynamic stability of water lubricated bearing-rotor system were performed on the aspects of critical speed, bearing dimensionless film composite stiffness, stability margin of logarithmic decay rate and the sudden unbalance response of excitation system. Physical and mathematical model were established to study the dynamic characteristics of the pump bearing-rotor system. The calculated first critical speed of the bearing - rotor system under rigid support and the modular elastic support was consistent with the stability condition. The values of dimensionless film integrated bearing stiffness, such as keq and γst were below zero, and the logarithmic decay rate of the first four modal analysis characteristic values at a rotational speed of 3000 r/min was greater than zero, which also demonstrate that the system was stable. This water lubricated bearing - rotor system was certified to be a stable system by responsive spectrum analysis on constant speed（500, 2 500, 5 000 and 10 000 r/min）, working speed (2950 r/min), and different starting acceleration suddenly adding exciting force. Therefore, this water lubricated bearing rotor system of high pressure multistage pump is a stable rigid system.