The effect of micro-beam plasma arc (MPA) surface remelting Ti alloy (Ti-6Al-4V) sheets was investigated. The results show that more satisfactory hardened layer could be acquired after MPA scanning process on TC4 titanium alloy. The composition, crystalline structure and micro-hardness in the remelted layer of TC4 were examined by OM, SEM, XRD and Vickers' micro-hardness tests, respectively. There were no micro-cracks or impurity in the treated sample after scanning by MPA. The micro-hardness of the treated samples was significantly improved as compared with the untreated substrates. X-ray diffraction results indicated that the surface remelting layer composed of phases, which was similar to the substrate. The micro-hardness of the surface was improved to 420 HV0.3 as compared to 190 HV0.3 of substrate. The increased hardness was obtained due to the micro-structural changes caused by rapid solidification owing to the self-quenching effect of the substrate after MPA remelting.