Disclosed is a method for preparing self-dispersing nano carbon black based on a thiol-ene click reaction. A sol-gel technique is used to graft a coupling agent containing a carbon-carbon double bond onto the surface of the carbon black, and a functional molecular chain is grafted onto the surface of the carbon black by a thiol-ene click reaction with a mercapto compound. The self-dispersing nano carbon black is obtained after centrifugation, washing and drying. The method is simple and easy to operate, has a high grafting rate, and can prepare self-dispersing nano carbon black adaptable to different systems by selecting mercapto compounds with different functional groups.