The invention relates to a nitrogen-doped graded pore graphene aerogel for a supercapacitor and a preparation method thereof, and belongs to the technical field of electrode materials. In the nitrogen-doped graded pore graphene aerogel, the nitrogen content is 3 to 2.3 wt.%, the specific surface area is 85 to 286m2/g and the electrochemical specific capacity is 51 to 228F/g l. Firstly, nanometer calcium carbonate @ polydopamine CaCO3 @ PDA particles were prepared. Secondly, CaCO 3 @ PDA particles, graphene oxide and thiourea were dispersed in deionized water, and graphene aerogels were prepared after freeze-drying. At last, that mixture is put into a tubular furnace to obtain the product. The graphene aerogel of the invention has the characteristics of graded pores; The preparation processis controllable; The prepared functionalized graphene was used as electrode material in supercapacitor, which was conducive to the electrolyte transport and wetting, and good electrochemical performance could be obtained.