The invention provides a preparation method of carbon nanotube powder with a low resistivity. The preparation method comprises the following steps: subjecting primary carbon nanotubes to a high temperature oxidation treatment in atmosphere, taking out fully oxidized carbon nanotubes, adding carbon nanotubes into an acid solution to carry out acid washing and soaking, after the requirements are met, washing the carbon nanotubes until carbon nanotubes become neutral, drying, saving carbon nanotubes for later use; doping halogen elements on the surface of dried powder, washing the powder to neutral, and drying the powder to obtain target product. The provided method can reduce the resistivity of primary carbon nanotubes with a high resistivity so as to improve the conductivity of the carbon nanotubes. The carbon nanotube powder can be used as the raw material of various composite materials.