The invention discloses a preparation method of a nano-nickel/array carbon nanotube composite material. The method comprises the following steps: using an array carbon nanotube as a cathode, and making nickel ions subjected to electrochemical reduction reaction on the array carbon nanotube at a certain current density to form the nano-nickel/array carbon nanotube composite material. The method provided by the invention uses the array carbon nanotube without any pretreatment on a metal foil as a substrate, obtains nano-nickel with controllable morphology and size on the cathode carbon nanotubeaccording to a constant current continuous electrochemical method, adopts closely linked steps, avoids a pretreatment process of the carbon nanotubes in the conventional method, and shortens the process flow; in addition, the constant current method is easier to control and easy to continuously and massively produce the nano-nickel/array carbon nanotube composite material. The method provided by the invention can effectively control the morphology and the size of the nano-nickel and the content of nickel by adjusting components and concentrations of the solution system, the current magnitude and the energization time, and is a simple, continuous and scalable preparation method of the nano-nickel/carbon nanotube composite material.