In order to verify the feasibility of a closed power flow vibration test bench about modification herringbone gear, a corresponding test bench was set up. A Herringbone gear vibration model with 24 degrees of freedom was established while considering the accompanying test gears, experimental gears and torsion shafts. The relative vibration acceleration influenced by torsion shaft stiffness was discussed, using herringbone gear with three-dimensional teeth modification as an example. The results consistently indicated that the relative vibration acceleration value of the teeth modification herringbone gear was influenced by torsion shaft and was 1.35% less than that of the given operating condition, so the closed power flow vibration test bench was applicable to the vibration experiment of the teeth herringbone gear transmission system. The influence between the paternity testing gear and experimental gear increased as the stiffness of the torsion shaft was enhanced. Thus, the stiffness of the torsion shaft should be as small as possible under the premise of system strength, transmission stability and layout requirement.