The invention belongs to the technical field of preparation of carbon nanomaterials, and provides a novel method for synthesising nitrogen-doped graphene by taking melamine as a main nitrogen and carbon source and methane as an auxiliary carbon source through a chemical vapour deposition method under the normal-pressure condition. Other catalysts, except for a metal substrate, and a conventional gas or liquid nitrogen source are not used in the method; therefore, the method is low in cost, non-toxic, simple and convenient to operate and convenient in process application; furthermore, no specific requirement for equipment exists in the reaction process; other heating devices, except for a main heating device, are unnecessary; therefore, the method is high in operability and is applied to practical popularization; the temperature of copper is slowly increased in the low-temperature stage at first; a nitrogen source and a carbon source are simultaneously introduced into a tubular furnace for one time when the temperature of copper reaches reaction temperature; then, the temperature is rapidly decreased to room temperature after completing reaction; at the time, a layer of nitrogen doped graphene film is formed on the surface of metal; and structural regulation and control, such as the doping amount and doping type of nitrogen in graphene and the thickness and crystallization degree of graphene, can be realized through the parameters, such as the optimized nitrogen source amount, temperature matching of front and rear temperature areas, the reaction time and the reaction temperature.