The invention relates to the field of preparation of carbon fiber aerogel materials, and particularly provides a preparing method of an aromatic heterocycle fiber-based nanometer carbon fiber aerogelmaterial. A technical problem to be solved is that carbon aerogel prepared by present methods is low in nitrogen content and poor in toughness. Aromatic heterocycle fiber dispersion is prepared from aromatic heterocycle fibers through a solution process, and is gelated through a method of promoting gelation with a reaction; then aromatic heterocycle fiber aerogel is prepared through a supercritical carbon dioxide drying process; and finally aromatic polyamide fiber-based nanometer carbon fiber aerogel is prepared through a carbonization process. Nanometer aromatic polyamide fibers contain thenitrogen element, and a certain amount of the nitrogen element can still be preserved in the carbon aerogel after carbonization, and therefore, in-situ doped nanometer carbon fiber aerogel can be directly produced by the method, thus laying a good foundation for preparation of an electrode material of a supercapacitor. The method is used for preparing the aromatic heterocycle fiber-based nanometercarbon fiber aerogel.