The invention discloses a preparation method of controllable nitrogen-doped carbon nanotubes. The method comprises the following steps: dissolving a metal salt, a carbon source and a nitrogen source in an aqueous or ethanol solution, performing stirring at 60-80 DEG C until the solution volatilizes to form a sol, drying the sol at 80-120 DEG C to form a gel, carrying out high-temperature heat treatment carbonization on the above gel precursor, keeping the temperature at 350-650 DEG C for 2-4 h, keeping the temperature at 750-1000 DEG C for 5-10 h to obtain nitrogen-doped carbon nanotubes containing metal or metal sulfide, and simply corroding the nitrogen-doped carbon nanotubes containing metal or metal sulfide to obtain the nitrogen-doped carbon nanotubes. The above sol-gel technology canrealize the effective regulation of the caliber and the length of the nitrogen-doped carbon nanotubes and the adjustment of the nitrogen content, the pore structure and the conductivity of the nitrogen-doped carbon nanotubes. The nitrogen-doped carbon nanotubes can effectively prolong the cycle life of a battery when applied to the electrode material of the battery, has good electrochemical performances, and is hopeful to be applied to fields of electrochemical catalysis, energy transition and energy storage.