The invention belongs to the technical field of chitosan composite materials and discloses an aramid nano-fiber modified chitosan composite film as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) adding aramid, an organic solvent, strong base and a dispersing aid into a container, heating, and uniformly stirring and dispersing, so as to obtain an aramid nano-fiber dispersing solution, wherein the organic solvent is a strong-polar organic solvent; and (2) adding chitosan-strong acid salt into the aramid nano-fiber dispersing solution, dissolving, carrying out film coating, adding the solution into a gel bath, standing, soaking into a cleaning agent, and drying, so as to obtain the aramid nano-fiber modified chitosan composite film. The composite film has excellent high-temperature resistance and thermodynamic property and relatively good film forming effect; and the preparation method is simple, a reagent is easily available and controllable, the cost is relatively low, and the industrial production is easily realized.