A new modelling method of gear-rotor system with multiple clearances used to investigate the dynamic responses of gear-rotor system is proposed. The dynamic model,including nonlinearity associated with radial clearance,dynamic backlash and time-varying mesh stiffness,is validated by experimental. Then the vibration characteristics of gear-rotor system with multiple clearances influenced by rotational speed and clearance size are presented and discussed in frequency domain. The results show that the spectrum of vibration acceleration mainly includes the radial frequency and mesh frequency. With the gradual increase of speed,the amplitude of radial vibration increases,and mesh vibration also more intense. The amplitudes of radial and mesh vibration increase with the increase of radial clearance. When the backlash is relatively large,the return difference is also relatively large. Finally,the theoretical calculation and analysis results are validated by the dynamic experiment data basically. And the differences between calculation results and experimental data are mainly from parameter error of dynamic model and measurement error.