Titanium carbonitride (Ti(C,N)) matrix cermets with different contents of nano-Si 3 N 4 particles have been fabricated by microwave sintering in nitrogen atmosphere. The addition of nano-Si 3 N 4 particle has important effect on the property of this cermet. Hardness and transverse rupture strength of the cermet are improved to about 1.3% and 25.2%, respectively, when the content of nano-particles is 2.0% in weight. Scanning electron microscopy (SEM) in combination with energy dispersive X-ray analysis (EDX) reveals that various cermets with or without nano-Si 3 N 4 present quite different morphological and structural characteristics. It may be because that the addition of nano-Si 3 N 4 particles inhibits the dissolution of Ti(C,N), and promotes the dissolution of WC and Mo 2 C in binder phase and the formation of the inner rim. The modified microstructure by the addition of nano-Si 3 N 4 particles results in the high mechanical properties of the cermet.