Ti6Al4V alloy surface was multi-alloyed by a double-glow plasma technique, and the homogeneous and dense Cr-Mo modified layer was formed. The phase structure and composition of the modified layer was characterized by XRD and GDOES, and its properties were tested by microhardness meter and ball-plate wear instrument. The results show that the composition in the modified layer are Cr and a few Mo, and decrease gradually from the surface to the underlying substrate. The layer is composed of Cr1.93Ti1.07, Cr2Ti, Cr2Ti4O11 and a few FeCrMo phase. Surface hardness of the modified Ti6Al4V alloy is increased greatly, and the wear resistance is improved significantly.