Abstract: The forced vibration problems of a turboshaft engine,which is mounted directly on the main gear box,were investigated.The characteristic of the engine structure and the source of the exciting force were analysed,and the distribution states of the axial force and bending moment caused by the vibration were also discussed.The mechanical vibration method and finite element method were applied to the forced vibration.The results of the full engine vibration experiment show that the proposed procedure is efficient.