The invention discloses application of a metal-free hydrogenation catalyst to catalysis of benzene hydrogenation. The metal-free hydrogenation catalyst used in the invention is a nitrogen-doped carbon nanotube prepared by using an impregnation method with melamine as a nitrogen source or prepared by using an in-situ synthesis method with ammonia gas as the nitrogen source, and is applied to benzene hydrogenation. According to the invention, the nitrogen-doped carbon nanotube is used as the benzene hydrogenation catalyst, is not loaded with any metal active component and achieves the purpose of hydrogenation catalysis only through modification by nitrogen doping; usage of precious metals is avoided in the whole reaction process, so cost is saved, the environment is not polluted, and the catalyst is reusable; and the catalyst is simple to prepare, low in cost, good in hydrogenation effect, easily controllable in reactions and friendly to environment, does not cause secondary pollution to environment and can be widely applied to a variety of hydrogenation reactions.