Based on the nonlinear bending-torsional coupling vibration mode of a NGW Planetary Gear Train, the meshing impact performance of the planetary gaear train is studied by using Runge-Kutta direct numerical integration method and some influence rules were gotten on the parameters such as composite meshing error and Power. The study results reveal that there are two error thresholds, one is small and another is big. The impact phenomenon will not appear if the composite meshing error value is smaller than the small error threshold. The unilateral impact phenomenon will appear if error value is bigger than the small error threshold but smaller than the big one. The bilateral impact phenomenon will appear if error value is bigger than the big error threshold. A small Power can more easily lead to unilateral impact phenomenon. Research results of this paper can provide some theoretical support to design a lower vibration noise, better running quality food machinery reducer.