Based on the Potts model, the grain growth of Si3N4 in liquid phase sintering process was simulated by Monte-Carlo method. A two-dimensional, square lattice is used to digitize the microstructure and the components and grain orientation are distributed randomly. The periodical boundary condition is applied. In the initial simulation, the grain growth and coarsening process driven by the reduction in interfacial free energy within a complex system involving a liquid phase were investigated with 32 orientations and different fraction of a liquid phase has been considered. Simulation was carried out with 200×200 lattice. The effects of the liquid amount on the grain growth mechanism and microstructures were discussed.