Abstract: The FEA model of a large-scale canned motor pump rotor is established based on ANSYS. The effects ofgyroscopic effect on the critical rotating speed and the mass unbalance response are investigated by using modalanalysis and harmonic response analysis. The analytical results show that the gyroscopic effect obviously affects crit-ical rotating speed and should be considered in the rotordynamic analysis. The calculated critical rotating speed ishigher than the design value when the gyroscopic effect is considered. The first resonant peak values of mass unbal-ance response in all test points are within the design vibration limit. The vibration amplitudes of the impeller, upperand lower flywheel centres far exceed other test points. These test points are susceptive to vibration and should bemonitored carefully in operation.