Abstract: The mechanism of interaction between a reactive armor and an incoming jet is further studied in the paper. A mathematical model for the disturbance upon the jet induced by the reactive armor during detonation is developed. The quantitative "Pebblestone model" is further simplified and quantized. Formulas for the computation of the period of forward-moving and backward-moving plates intercepting the incoming jet are derived. Methods of computation of the jpenetration depth of jet after disturbance and that of the disturbing efficiency are provided, and a comparison with the experimental results is undertaken.