In allusion to a truck transmission frame, using finite element method, its modal analysis and randomly vibration simulation analysis is conducted based on ANSYS software. According to the results of modal analysis, Power Spectral Density of random vibration was carried out. Related strength and deformation parameters of the truck frame were obtained through analysis. The calculation result has important reference meanings to the frame of the design modifications and finalizing the design and trying type. The calculation method used in the paper can also be used in calculation of other random vibration system.