The invention provides a carbon nano material/metal nano material composite nano ink which comprises solvent, an additive, a carbon nano material and a metal nano material. The carbon nano material/metal nano material composite nano ink is characterized in that the solvent can comprise water, alcohol organic solvent (ethanol(alcohol), isopropanol, n-butanol and the like), ester organic solvent (ethyl acetate, butyl acetate, ethylene-propylene acetate and the like), benzene organic solvent (methylbenzene, dimethylbenzene and the like) and ketone organic solvent (cyclohexanone, acetone, methylethylketone, butanone and the like); the additive comprises surfactant, pH value stabilizer, defoaming agent, diluter, reinforcer and the like; the carbon nano material comprises a single-layer carbon nanotube, a double-layer carbon nanotube, a multi-layer carbon nanotube and graphene; the metal (copper, silver, gold, platinum, nickel and the like, also including an alloy nano material, an ITO metal composite nano material and the like) nano material further comprises a metal nanoparticle, a metal nanowire or a metal nanotube; the components of the nano ink must include one carbon nano component and one metal nano component, such as a single-layer carbon nanotube and copper nanowire composite ink, a double-layer carbon nanotube and silver nanowire composite ink, a single-layer carbon nanotube and silver nanoparticle composite ink or any other possible combination; the components can be regulated according to specific applications; and a composite nano conductive film can be formed on different bases through different electronic printing processes. The ink can be used in the printing of a flexible base material and can be conveniently prepared into a flexible conductive film.