The field emission cathode coating of nano-diamond on titanium substrate were prepared by electrophoretic deposition, the hydrogen plasma process was carried out after heat treatment, and then the microstructure , field emission properties and the luminescence performance of the samples were characterized. The results show that the adsorption of H+ and the etching of H+ collectively affect the morphology of diamond coating. Deficient hydrogen treatment can’t reach the requirement and excessive hydrogen treatment can lead to serious etching for the diamond coating, which resulting in worse field emission properties of the coating and luminescence effect. The appropriate hydrogen treatment is helpful to improve the field emission properties and luminescence effect. Finally, the field emission mechanism of nano-diamond coating on titanium substrate was discussed, and the reasons of luminescence effect were explained.