Abstract: The effect of the size of the second phase particles on grain growth was investigated by phase field model in this model. The critical pinning size when the second phase particles effectively bind the crystal boundary at different contents was determined. The results show that most of the second phase particles are located at the grain boundaries and the particles have a strong pinning effect on the grain boundaries during the microstructure evolution. With a certain particle size fraction, the larger the particle size, the stronger the pinning effect of an individual particle, but the total pinning effect is weaker, and the average size of the grains is larger when reaching the stable annealing state at a certain. The larger the volume fraction of the particles, the larger the critical size of the second phase particles. The relationship between the limit grain radius, the second phase particle radius and the particle content can satisfy the Zener relationship.