Cobalt-containing amorphous carbon composite films have been prepared by filtered cathodic vacuum are technique (FCVA) with a cobalt-containing graphite target on nickel-coated Coming glass at room temperature. After heat treating at 550 degreesC in a mixture of acetylene and nitrogen gases, field emission-properties of the a-C:Co films were significantly improved. Relatively uniform emission sites and a low threshold electric field of 2 V/mum were obtained without conditioning. The relatively low threshold held is probably attributed to both the graphitization of the composite films caused by cobalt catalyst and modified surface conditions by the heat-treatment process. Moreover, the heat-treated samples still remained a smooth surface with a root mean square roughness of about 22 nm, which could be possibly used to prepare gated carbon emitter array for field emission display.