Mo modified layers on Ti-6Al-4V alloy were obtained with plasma surface alloying technique. The properties of the Mo-diffusion layers were investigated in this paper. Results show that the Mo-diffusion layers obviously enhance the wear resistance of Ti alloys against a polished 2100 steel counterbody ball under ball-on-disc test condition. With a series of experimental results, a wear model of high wear resistance of modified layers is propounded. The noval wear behavior is a result of absolute elasticity characteristics on the subsurface of Mo modified layers.