The dynamic loading due to blasting vibrations often leads to local instability of the highly-stressed tunnel and the rock burst during mining. Based on the elasticity and the stress wave theory, the mechanism of the instability and the crack development due to the dynamic vibrations in the highly-stressed tunnel are analyzed. In order to see why the highly-stressed tunnel in Yongshaba mine might be severely destroyed by dynamic vibrations, the numerical simulations of the highly-stressed tunnel under dynamic loading are carried out with the particle flow software PFC^2D, and the effects of the disturbance stress wave intensity on the stress fields, the displacement fields and the crack fields in the surrounding rock are investigated by varying the peak value of the dynamic loading. The static and dynamic calculations are carried out, separately. The results show that the extents of the stress fields, the displacement fields and the crack fields in the surrounding rock under a dynamic disturbance will increase obviously as compared to the static calculation results. The higher the disturbance stress wave intensity, the more significant the dynamic disturbance influences on the stress, displacement and crack fields both in the roof and the floor of the tunnel will be. Several suggestions are made to avoid the instability and the subsidence of the highly-stressed tunnel induced by the dynamic disturbance.