The random vibration due to road roughness has some effect on mobile manipulator. The reliability and the stability are reduced. First vibration dynamic model of the mobile plat is built by the Lagrange model, and the dynamic model of the manipulator is built with finite element method (FEA). And then the two models are rebuilt into whole model of the mobile manipulator by the force balance on the common point. Using the accurate and highly efficient pseudo-excitation method (PEM), precise time-integration and the vibration dynamic model, the transient power spectral density (PSD) of vehicle in non-stationary random vibration excitation is obtained. This result can give a valuable reference to design the suspension of the mobile manipulator.