Abstract: Various stagnation effects of grain growth in nanocrystalline materials have been found, but thickness effect is hardly investigated. This paper presented an anisotropic Monte Carlo (MC) algorism to stimulate grain growth in nanofilms with different thicknesses in annealing process. The simulation results reveal that thickness effect begins to be exhibited only when the average grain size reaches 0.8 to 1.2 times of the thickness of the films, not in the whole process of grain growth. Through introducing thickness factor, the paper modified Burke’s grain growth kinetic model and obtained a new equation in better accordance with the simulation results as well as the physical model of thickness effect.