By using high energy ball-milling and vacuum hot-pressed sintering techniques, ultrafine grained carbide cement WC-2.5TiC-10Co were prepared, and the effect of grain growth inhibitors Cr₃C₂, VC, TaC and NbC on microstructures and mechanical properties were studied by X-ray diffractometer, field emission scanning electron microscope (FESEM) and mechanical performance test. The results indicates that the particle size of the WC powder can be reduced to less than 0.2 μm from 0.6 μm after 30 h of high energy ball-milling at a rotation speed of 350 r/min and ball/powder ratio of 10: 1. After vacuum hot-pressed sintering at 1410℃ for 1h, no new reactive product formed revealed by XRD. When 0.45 %Cr₃C₂, 0.3 %VC, 0.5 %TaC or NbC were added to the carbide cement, a small quantity of abnormally coarsened WC grains occurred, while the fractured surfaces display loose and smooth. Analyzing the fractured surfaces indicate that cleavage cracking in coarsened WC grains was caused by concentrated stress and become the source of materials fracture. When the contents of inhibitors Cr₃C₂ and VC were both more increased 0.1%, the grain size of WC can be reduced less than 0.5 μm. In such a case, the fractured surfaces are intimate and step-like, while the bending strength can be increased by 20%. Inhibitors TaC and NbC have not pronounced effect on the preventing the WC grain growth, while the addition of NbC is most effective in improving the relative density of the carbide cement.