There are two interaction mechanisms between shaped charge jet and thin flying plate driven by explosion, that is, the intermittent and continuous disturbance. Determination of the transition criteria for the intermittent and continuous disturbance is of importance for the penetration calculation of the escaping jet and the design of ERA(explosive reactive armour). In this paper a new criteria was presented based on the analysis of interaction process, and the effects of NATO angle and thickness of flying plate on the disturbance frequency were discussed. It is shown that the critical shaped charge jet velocity increases with the plate thickness and NATO angle, especially increases drastically between 45� and 60�.