The effect of adding nano-scale alumna on mechanical properties and microstructure of micron-scale Ti(C,N) matrix cermet tool materials were investigated,which based on the mechanisms of grain improved fracture toughness.The results show that the mechanical properties of Ti(C,N) based cermet are greatly influenced by adding nano-scale alumna,especially the hardness and fracture toughness improved significantly.At the same time the disadvantages of low hardness and fracture toughness of Ti(C,N) ceramic cutting tool materials are eliminated.The microstructure observation and analysis by SEM show that Ti(C,N) grains are fined by nano-scale Al2O3 particles,and transgranular fracture mode of the material is mainly observed.The improvement of mechanical properties is due to the transformation of fracture mode and fining of Ti(C,N) grains.