A competitive lattice model was developed for the Kinetic Monte Carlo (KMC) simulation of the competition of 4H and 6H polytypes in SiC crystal growth based on the on-lattice model. In the competitive lattice model, site positions are fixed at the perfect crystal lattice positions without any adjustment of the site positions. The effect of surface steps was investigated, and behavior similar to step-controlled homoepitaxy was observed in KMC simulation of PVT grown SiC. Maintaining the step growth mode is an important factor to maintain a stable single polytype during SiC growth.