In order to study the coupling vibration characteristics between the carbody and power package structure and calculate thecarbody inherent frequency and low-order type, the urban rail vehicles coupling vibration model with power pack structure hanging underthe carbody was derived, and the influence of hanging parameters on character of carbody vibration was analyzed. The results showedthat: the influence of the first order vertical bending frequency of carbody on vertical stability was larger than the second order; when thevibration of the power package was input to model as periodically excited, and the excitation frequency reached 9.5 Hz or 16.5 Hz,whichwould superimpose with the first and second order benging frequency range, the ride index rapidly deteriorated. Therefore, vehicle designshould try to avoid these resonance frequencies.