In this paper, the first principle method based on density functional theory is adopted to establish the interface model of WC/WC-Co through the software Materials Studio (MS). On the basis of this interface structure, rare earth element Y is doped, and then the energy of WC/WC-Co before and after doping is calculated respectively. The electronic structure is analyzed, and the calculation results of the two structures are compared. Finally, the grain growth is simulated by cellular automata of matlab to verify our calculation and analysis results. The results show that the interfacial adhesion work increases and the interface structure is more stable after doping Y element. The interface energy decreases and plays a role in grain refinement.