Amorphous carbon nanoparticles (a-CNPs) on a multi-walled carbon nanotube (MWCNT) film, deposited on a silicon substrate, were synthesized using an electrodeposition combination from a methanol suspension of polydiallyldimethylammonium chloride-modified MWCNTs. A low-voltage electrophoretic deposition of the MWCNTs and a high-voltage electrochemical deposition of the a-CNPs were carried out to yield homogenously attached a-CNPs on the surfaces of the MWCNTs, and form a composite film with good adhesion to the substrate. This scalable technology can produce a large area of a-CNP/MWCNT film. And the field emission investigations show that the a-CNP/MWCNT film has turnon electric field of 3.17 V µm^_1 (at 10 µA cm^_2) and threshold field of 4.62 V µm^_1 (at 1 mA cm^_2), which are lower than those of the MWCNT film. The a-CNP/MWCNT film can be deposited simply with large areas and may be a promising cathode material applied in field emission displays.