Abstract: The web structure has been widely used in design of aviation gears,and its structure vibration has attracted much attention.But the function of web as a torsion spring in the dynamic behaviour of gear system needs a thorough investigation still.In this paper,a typical gear transmission is taken for example,its dynamic model has been built up to analyze the vibration mode of the system.The dynamic responses of this system at various speeds have been obtained with Fourier method by considering the transmission error of the pair of gears as excitation.Further,the influences of web flexibility and attached damping on the dynamic responses have been studied,the dynamic loads on the teeth when the web thickness is changed,and the damping,both attached and unattached,have been calculated respectively.Some useful conclusions have been drawn which show that the combination of flexible web and attached damping can lower the vibration level and decrease the dynamic loads obviously.