The invention provides an organic carbon nanosphere lubricating oil additive and its preparation method and application, comprising the following steps: S1, dissolving the reaction monomer in the reaction solvent, after mixing fully, placing it at a temperature of 0-90°C, and reacting 3 ~12h, obtain the organic carbon precursor of the polymer; wherein, the reaction monomer is a small molecule compound that can be polymerized into a hypercrosslinked π-bonded conjugated polymer; S2, combine the organic carbon precursor obtained in step S1 with All doping sources are placed in a tube furnace for doping and carbonization to obtain organic carbon nanospheres containing doping sources; wherein, the doping sources are one or more of N sources, S sources, and P sources. By synthesizing organic carbon sources and simply carbonizing and doping N, S, P elements, the dispersion stability of carbon nanosphere additives in base oil can be significantly improved, and N, S, P doping can improve the dispersion stability under high loads. wear resistance.