The work aims to improve the hardness and wear resistance of powder metallurgy gear through surface plasma W-Mo alloying. The W-Mo alloy coating was prepared on the surface of powder metallurgy gear by double glow plasma surface metallurgy technology. The surface morphology and chemical composition of the W-Mo alloy coating was characterized by scanning electron microscope (SEM) and energy dispersive X-ray spectroscope (EDS). The microhardness of the substrate and W-Mo alloy coating was measured by Vickers microhardness tester. The effect of plasma W-Mo alloying on the abrasion resistance of powder metallurgical gears was studied by reciprocating friction and wear experiments under different loads. The W-Mo alloy coating was successfully prepared on the surface of powder metallurgy gear by double glow plasma metallurgy technology. The alloy coating was metallurgically bonded with the substrate. The average microhardness of substrate increased from 145.8HV0.1 to 344.4HV0.1 after double glow plasma surface W-Mo alloying, an increase of about 2.4 times. The friction and wear tests under different loads indicated that the friction coefficient declined from 0.6~0.7 to about 0.45~0.5 after W-Mo alloying, a decrease of about 30%. With the increasing of the load, the wear volume of the substrate and the W-Mo alloy coating increased. The specific wear rate decreased from 18.70×10?5~36.16×10?5 mm3/(N.m) of the powder metallurgy gear to 2.99× 10?5~8.79×10?5 mm3/(N.m) of the W-Mo alloy coating, which was a decrease of about 74%~84%. The wear mechanism of the substrate consisted of adhesive wear and abrasive wear, while wear mechanism of the W-Mo alloy coating was slight abrasive wear. The W-Mo alloy coating improves the hardness and wear resistance of powder metallurgy gear significantly. The surface plasma W-Mo alloying technology provides a new technical method for the surface strengthening of powder metallurgy gear.