The invention relates to an expandable preparation method of a high-density N-doped graphite material, which includes steps of mixing GO dispersing fluid with PEI solution to obtain GO-PEI composite;drying and roasting the GO-PEI composite. An amino functional group of the PEI can reduce the GO oxygen content on a certain degree and effectively stop the thermal expansion caused by decomposing massive oxygen-containing functional groups to be gas during the process of roasting the samples, so that the material density is greatly reduced. The vibration density of the material and the balance regulation of the surface area can be realized by controlling the PEI addition. The reaction process is free from adding metal salt type pore forming substance or activating reagent; thus the original framework structure of the graphite can be well kept, and the operation step is simple and easy to carry out.