Abstract: By using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and measuring mechanical behaviors, microstructures of WC and Co powders with different initial particle sizes are investigated after different times of ball milling. The ball milled composite powders with different percentage of grain growth inhibitors are vacuum hot-pressed and sintered to prepare ultra-fine grained cemented carbides and the microstructure and mechanical properties of the as-prepared cemented carbide are studied to reveal the effect of grain growth inhibitors of different proportions. The results show that the ultra-fine raw powder material has a good effect after a short time of ball milling; the grain refining effect in cemented carbide by adding VC+Cr₃C₂ or VC+TaC is better than that of the sole adding of VC; the WC particles has a near round shape and the bending strength of the cemented carbide can be improved by adding Cr₃C₂; the WC particles take shapes of triangle or quadrilateral after adding Tac which can improve the hardness of cemented carbide.