The invention discloses a preparation method of a carbon nanotube film. The method comprises the following steps: (1), putting carbon nanotubes into a graphitization furnace, vacuumizing and heating the carbon nanotubes to over 2800 DEG C, carrying out heat preservation for a period of time, and then cooling the carbon nanotubes to a room temperature; (2), with the carbon nanotubes in the step (1), a dispersing agent, a binder and an N-methyl-2-pyrrolidinone solution as raw materials, carrying out ultrasonic treatment, high-speed shearing or ball-milling and the like to prepare a carbon nanotube suspension; (3), dropwise adding the carbon nanotube suspension in the step (2) on a paved base, drying the carbon nanotube suspension at 65 DEG C and separating the base; and (4), putting the carbon nanotube film in the step (3) in a vacuum furnace and heating the carbon nanotube film with the furnace to 1300-1500 DEG C for carbonization, carrying out heat preservation for 0.5-2 hours, cooling the carbon nanotube film to the room temperature and taking out the carbon nanotube film. The carbon nanotube film prepared by the method is about 10-20[mu]m in thickness; the base is relatively easy to separate; through high-temperature carbonization and modification, the carbon nanotube film has relatively good usability, is capable of replacing an aluminum foil and a copper foil as a current collector in a lithium ion battery, can be independently used as an anode, and has relatively high initial specific capacity.