Abstract: In this paper a new model of the drop breakage in a vibrating plate tank has been developed by a me-chanism based on the shearing stress in the neighborhood of the holes in the plates as a breakage force,andthe coalescence of drops may be dealt with by the process of gas molecule collision.Based on the theoreticalanalyses,simulation of drop breakage and coalescence which are random processes has been carried out byMonte-Carlo simulation technique.The parameters of breakage and coalescence rate have been obtained.