A carbon nanotube composite preform includes a substrate and a plurality of carbon nanotubes formed thereon. Each carbon nanotube includes a first end adjacent to the substrate and a second end away from the substrate. Gaps between the second ends of the carbon nanotubes are bigger than gaps between the first ends thereof. The method for making the carbon nanotube composite preform includes the following steps: (a) providing a substrate; (b) forming a plurality of carbon nanotubes (e.g., a carbon nanotube array) on the substrate; (c) placing the carbon nanotubes and the substrate in a solvent for some time; (d) removing the carbon nanotubes and the substrate from the solvent; (e) drying the carbon nanotubes and the substrate to form a carbon nanotube composite preform.