A preferred method for making a carbon nanotube-based field emission cathode device in accordance with the invention includes the following steps: preparing a solution having a solvent and a predetermined quantity of carbon nanotubes dispersed therein; providing a base with an electrode (101) formed thereon; forming a layer of conductive grease (102) on the base; distributing the solution on the layer of conductive grease, and forming a carbon nanotube layer (103) at least attached on the surface of the conductive grease after the solvent evaporates; and scratching the layer of conductive grease, in order to raise first ends of at least some of the carbon nanotubes from the conductive grease and thereby attain an effective carbon nanotube field emission cathode.