By analyzing the vibration movement of the gear system

the relative-slide movement between the meshing gear surfaces with or without considering the systemic vibration is demonstrated;the abrasion failure mechanism of the gear due to the vibration of the gear system is revealed.It is pointed out that the theoretic meshing line and the practice center line of the meshed gears is vary with the plane motion

and the locus of practice meshing point is not a line but a curve because of the vibration.It is also pointed out that the vibration have the meshing point on the partial of gear surface（generally

the middle of the surface） moved with reciprocation of two foot ahead and one foot back.It’s this reciprocation of meshing point that damages oil membrane and increases the shock

the relative-slide and the rub between the meshing gear surfaces.All of this result in intense slide frictions between the meshing gear surfaces

and therefore cause worn early.