A dynamic similitude design method is proposed for the problem of sudden unbalance of the rotor system. The dynamic differential equation requires the application of both equation analysis and dimensional analysis methods to establish the scaling laws， while also considering the damping scaling ratio. Based on the strain energy distribution criterion， a prototype rotor system is designed. The prototype is scaled according to the scaling laws to create a distorted model， and the dynamic similarity between the prototype and the distorted model is verified through simulation and test. The simulation results show that the distorted model ex? hibits high similarity to the prototype in terms of critical speed， strain energy distribution， and transient response. The errors for the first two critical speeds are 0.1% and 0.13%， respectively， and the error in peak amplitude is 3%. The test results show that the distorted model can accurately predict the critical speed and sudden unbalance vibration response of the prototype， with the errors for the first two critical speeds being 0.79% and 1.72%， respectively， and the error in peak amplitude being 5.98%.