The invention belongs to the technical field of carbon aerogel which is a nano-porous material, and particularly relates to graphene nanoribbon/carbon nanotube cross-linked polyimide-based compound carbon aerogel and a preparation method thereof. The method includes the steps of preparation of an oxidized graphene nanoribbon/carbon nanotube hybrid material, synthesis of water-soluble polyamide acid, sol-gel method preparation of oxidized graphene nanoribbon/carbon nanotube/polyamide acid aerogel, preparation of graphene nanoribbon/carbon nanotube/polyimide compound carbon aerogel, activating treatment, high-temperature carbonization and the like. The method is easy to implement, low in cost and environmentally friendly. Prepared graphene nanoribbon/carbon nanotube/polyimide-based compound carbon aerogel has the advantages of being large in specific area, high in porosity, uniform in pore size and distribution and the like and can serve as a catalyst carrier material, an adsorbing material and an electrode material of supercapacitors, lithium ion batteries and other new energy devices.