Abstract: Aiming at the problem of low cutting quality caused by vibration of shrub cutting machine, the external excitation of cutting device was simulated by installing mass block on the edge of saw blade cutter, and the relationship between simulated quality and cutting device vibration was proved by mechanical calculation. Through finite element modal analysis of cutting device and forced vibration comparative analysis of saw blade with or without external excitation, the vibration characteristics of cutting device were investigated. Finally, the influence of external excitation and feed speed on cutting force was investigated through virtual prototype experiment. The results showed that the centroid vibration of the saw blade was mainly axial vibration. At 7.34 Hz, the excitation frequency was close to the natural frequency of rigid body dynamics, and the resonance was generated. The amplitudes of the saw blade was 141 mm under the action of external excitation and 56 mm without the action of external excitation. The fitting curve equation of vibration mass and cutting force under simulated external excitation were simulated, and the fitting effect was good. The results showed that the vibration generated under external excitation and the feed speed had influence on the cutting force, and the vibration influence under external excitation was more significant.