WC nanosized powders are synthesized by the plasma arc discharge process and annealing under an inert (Ar) atmosphere. The high temperature used during discharging at local region causes the work-piece and electrode to melt and evaporate. The melted tungsten on the arc discharge electrode and carbon arising from decomposition CH4 gas forms WC1-x nanosized powders. The WC1-x phase is encapsulated in a amorphous carbon shell. The WC1-x nanosized particles are annealed at 1200~1400°C under an Ar atmosphere. The WC1-x nanosized powder is transformed to the W2C phase, and then it becomes WC above at 1400°C.