Disclosed is a preparation method of nitrogen-doped graphene-loaded metal single atom catalysts. As a compounding agent, ethylenediamine tetraacetic acid disodium salt is subjected to an ion exchange reaction with metal ions in liquid phases to form a stable compound, the compound is fully and evenly mixed with alkali metal salt after drying by distillation, and the nitrogen-doped graphene-loaded metal single atom catalysts are obtained through simultaneous pyrolysis conversion. The prepared catalysts have the appearance characteristics of two-dimensional microstructures which are super-thin and large in area, the thickness is 0.5-2 nm, the number of graphene layers is 1-8, the metal load is within 0.01-10 wt%, and the catalysts can be applied to the field of catalysis synthesis of energy, catalysis, medicine and biology. The method can be widely applied to the synthesis of various metal single atom catalysts, obtained metal single atoms can all be firmly riveted on the surface of graphene, the load amount is high, and the thermal stability is good. The method has the advantages of being simple and safe in operation process, low in cost, controllable to prepare, large in synthesis amount, suitable for industrialized production and large-scale application and the like.