Abstract: Mo penetration was carried out in the surface of TC4 alloy by double-glow plasma metallurgy technology. The friction and wear properties of the alloy before and after Mo penetration were studied at sliding speeds of 10, 20 m·min-1. And the phase composition and micro-hardness of Mo modified layer were investigated, the wear mechanism of the Mo modified layer was also analyzed. The results showed that a Mo modified layer in the surface of TC4 alloy was obtained after plasma Mo penetration, which was 30 μm in thichness and 1 107.8 HV in hardness, with a gradient Mo distribution. The wear resistance of TC4 alloy was significantly improved due to the high surface hardness of Mo modified layer and the complete oxide film on surface of wear trace. When the sliding speed changed from low speed to high speed, the wear volume and the specific wear rate of the Mo modified layer all increased, because the ploughing effect and wear became more serious.