MacPherson-Srolovitz's three-dimensional grain growth rate equation proposed recently by MacPherson and Srolovitz indicates that the change rate of grain volume depends on the mean width of grains and the total length of the triple lines. This rate equation is studied by large-scale Potts model-Monte Carlo simulation in this paper. The result shows that the data of averaged grain growth rate fit the MacPherson-Srolovitz’s three-dimensional grain growth rate equation very well, thereby this rate equation is preliminary verified.