The titanium and tungsten were used as the transition layer respectively, the mirco-crystalline diamond films on a silicon substrate were prepared by PE-HFCVD method. The field emission characteristics of the films were studied in this paper. The results show that, the metal transition layers can significantly enhance the field emission properties of the diamond films. When the transition layer is tungsten, the opening field intensity of the diamond film is 5.4 V/μm, which reduces by 44% compared with non-transition layer ; while the field emission current density can reach 1.48 mA/cm₂ when the electric field intensity is 8.9 V/μm. The structure characterization of the films show that, The enhancement of the field emission properties is mainly attributed to the decrease of the electron transport barrier at the interface and the increase of the sp₂ C content in the film. The formation of good conductive channels at the interface and the diamond film make the electron more easy to transport to the film surface. Hence, the diamond films which use metal transition layers show excellent field emission properties.