The invention discloses a surface treatment method for improving the welding properties of Al2O3 ceramic and Ti6Al4V alloy. The method comprises the following steps: (1), preparing Ni-Ti alloy layer on the surface of the Ti6Al4V alloy from a Ni-Ti alloy target material by adopting a double glow plasma surface metallurgy method, wherein the Ni-Ti alloy layer comprises a Ni-Ti deposition layer and an inter-diffused layer; (2), injecting Ti ions on the surface of the Al2O3 ceramic through an ion injection method; and (3), welding the Ti6Al4V alloy prepared in the first step and the Al2O3 ceramicsubjected to surface treatment in the second step in vacuum diffusion welding equipment. The method can directly realize vacuum diffusion welding between the Al2O3 ceramic and the Ti6Al4V alloy through the treatment of the double glow plasma surface metallurgy method and the ion injection method, is high in efficiency, and can greatly improve the application of vacuum diffusion welding to the welding technology of the Al2O3 ceramic and the Ti6Al4V alloy.