In view of cantilever multistage centrifugal pump in operation process is prone to vibration of shafting and bring reliable and stability problems, due to its unique suspension center cantilever rotor structure. The rotor axis trajectory of cantilever multistage centrifugal pump was explored under design flow through combination of numerical simulation and experimental verification. Cantilever multistage centrifugal pump rotor dynamic characteristics in the operation was not only influenced by the uneven quality of unbalance mass, but also influenced by sealing fluid excitation force, fluid excitation force induced by chamber and fluid added mass. The dynamic model of the cantilever multistage centrifugal pump was simulation with the above calculation results so that the influence of sealing fluid excitation force, fluid excitation force induced by chamber and fluid added mass on the rotor axis trajectory could be calculated. Furthermore, the simulation results were compared with those of the model without sealing fluid excitation force, fluid excitation force induced by chamber and fluid added mass, the model with sealing fluid excitation force only, the model with both sealing fluid excitation force and fluid excitation force induced by chamber and the model with all excitation. Finally, the simulation was verified by the test of rotor axis trajectory. The results showed that the sealing fluid excitation force of the ring of impeller improved the stability of system, compared with the rotor with no sealing excitation force, and reduced the radial displacement amplitude. Fluid excitation force induced by chamber increased the cross stiffness of rotor system led to an increase in the amplitude of vibration. Fluid added mass compared with sealing excitation force and fluid excitation force induced by chamber had a remarkable effect on transient response of cantilever rotor system and the magnitude of displacement nearly gapped two orders of magnitude. The research provided reference for improving the operation stability of cantilever structure optimization of multistage centrifugal pump.