Study on simulation method for the thin film growth processes on atomic scale is currently a hot research field. The simulation method mainly aiming at nanometer scale model demands huge computational cost and memory cost. In order to solve the problem, a cellular method combined with Monte Carlo method is presented in this article to simulate the growth processes of thin film on micron scale. Based on cellular method for model representation and evolutionary computation, we greatly reduce the memory requirements and improve the efficiency of computation, and the Monte Carlo method is used to determine the particle migration. Moreover, specific research on the growth process of silicon nitride thin film is implemented, and the simulation results are compared with the experimental data and the molecular dynamics simulation results of the surface morphology and composition, so as to verify the effectiveness of this method.