An apparatus for making an array of carbon nanotubes includes a reaction chamber with a gas inlet and a gas outlet; a quartz boat disposed in the reaction chamber; a substrate with a surface deposited with a film of first catalyst, the substrate being disposed in the quartz boat; and a second catalyst disposed in the quartz beside the substrate. A method for making an array of carbon nanotubes, comprising the steps of: (a) providing a substrate with a surface deposited with a film of first catalyst; (b) disposing a second catalyst beside the substrate to produce small amounts of hydrogen gas which flows to the first catalyst; (c) introducing a carrier gas and a carbon source gas flowing from the second catalyst to the first catalyst at a predetermined temperature; and (d) growing an array of carbon nanotubes extending from the substrate.