The invention belongs to the technical field of electrodes, and particularly relates to carbon nanotube array slices with precisely controlled length and diameter and a preparation method and application thereof. The preparation method comprises the following steps: growing an orientated carbon nanotube array by a chemical vapor deposition method; by taking the orientated carbon nanotube array as a template and taking ethylene as a carbon source, growing a coaxial graphene layer on the surface of the orientated carbon nanotube array by the chemical vapor deposition method, thus obtaining an orientated carbon nanotube array with a core-shell structure, wherein various heteroatoms can be introduced in a doping way in the growth process; finally cutting the carbon nanotube array along a diameter direction in a freezing slicing way, and regulating and controlling feeding distance to obtain the highly controllable carbon nanotube array slices. By taking the carbon nanotube array slices as an electrode material, a prepared lithium ion battery has excellent energy storage property, and the specific capacity of the battery can reach 2450mAh/g maximally.