A method for measuring a growth rate of a carbon nanotube includes the following steps: (a) providing a substrate (12); (b) forming a catalyst layer on the substrate; (c) heating the substrate to a predetermined temperature; (d) intermittently introducing/providing and then interrupting a reaction gas proximate the substrate to grow a patterned carbon nanotube array, each carbon nanotube having at least one line mark formed thereon as a result of the patterned growth; and (e) calculating the growth rate which is equal to a length between a pair of line marks divided by a time interval between said two line marks.