In this work, a novel lightweight AlCrTiNbMo refractory high-entropy alloy (RHEA) coating has been developed to overcome the surface damage defects in Ti-6Al-4V alloys under wear and erosion conditions. A crack-free in-situ nitride (AlCrTiNbMo)Nx RHEA coating were successfully prepared by the gas assisted laser nitriding. According to XRD, SEM and TEM analysis, AlCrTiNbMo coating was composed of single BCC phase, while (AlCrTiNbMo)Nx coating was constituted by BCC and TiN phases. The average microhardness of AlCrTiNbMo and (AlCrTiNbMo)Nx RHEA coatings were 591.2 HV0.3 and 1070.1 HV0.3 respectively. (AlCrTiNbMo)Nx RHEA coating has lower friction coefficient and wear rate than AlCrTiNbMo RHEA coating and the substrate from room temperature to 600 ℃. At 600°C, (AlCrTiNbMo)Nx RHEA coating showed a rare self-lubricating behavior, the friction coefficient decreased to 0.275 (61.9% of the substrate), and the wear rate was 0.06 mm3/N·m×10-4 (1.24% of the substrate). The erosion rates of (AlCrTiNbMo)Nx RHEA coating at erosion angle of 30°, 60° and 90° were 11.0%, 22.3%, and 36.8% of those of the substrate, respectively. The homogeneous and hard TiN array-BCC structure generated by in-situ self-reaction was the main factor for the excellent wear and erosion resistance of (AlCrTiNbMo)Nx RHEA coating. Thus, (AlCrTiNbMo)Nx RHEA coating and corresponding laser nitride technique were expected to be applied in the severe working environment of high temperature, wear, and erosion.