In the vibration detection of multi-stage gear transmission, the gear ratio has a regular influence on its vibration characteristics. To explore this phenomenon, this paper presents the phase configuration method of the multi-stage gear transmission. The complete mesh phasing space based on the system gear ratio and the phase between each stage is derived. Taking The two-parallel shaft gear transmission system as an example, A nonlinear dynamic model is established. The influence of phase configuration on the vibration characteristics is analyzed in detail. By means of the numerical calculation method, the vibration equation is solved for the gear system, and the varying regularity of the optimal phase angle of the vibration characteristics at different mesh frequency was found. Finally, it reveals the influence of different gear ratios on the vibration characteristics of multi-stage gear transmission.