The invention discloses a method for preparing aluminum-doped carbon nanotubes. The method comprises the following steps: putting a catalyst and an aluminum foil substrate into a tubular furnace heating temperature zone; sealing the tubular furnace heating temperature zone, introducing a first mixed gas into the sealed area, increasing the temperature of the tubular furnace heating temperature zone to an appointed temperature value, and performing a reduction reaction; after the reduction reaction is completed, introducing a second mixed gas into the sealed area, and performing growth of carbon nanotubes at an appointed temperature value; and peeling the grown carbon nanotubes from the aluminum foil substrate, so as to complete preparation. By adopting the method disclosed by the invention, an aluminum metal is introduced for doping modification treatment in a carbon nanotube preparation process, and the gas sensitivity of a carbon nanotube material can be improved to a large extent.