To improve the mechanical properties of high-energy TEGDN gun propellants, based on high-energy TEGDN gun propellant formulations, adding a small amount (mass fraction of 0.5%, 1.0%, 1.5%, 2.0%) of cellulose nanofibers (CNFs) obtained from lignocellulose, high-energy TEGDN gun propellants containing CNFs were prepared. The surface structure and thermal decomposition property of high-energy TEGDN gun propellants before and after adding CNFs were studied by scanning electron microscopy, thermogravimetric analyzer and differential scanning calorimeter. The impact strength and energy performance of high-energy TEGDN gun propellants containing CNFs were studied by the Charpy impact testing machine and closed bomb vessel test. The results show that adding a small amount of CNFs can obviously improve the low-temperature impact strength of high-energy TEGDN gun propellants and very little on thermal decomposition performance. Compared with the original high-energy TEGDN gun propellant (reference sample), the impact strength of high-energy TEGDN gun propellant of adding 0.5% CNFs increases by 30.4% under the low temperature of -40 ℃ and increases by 8.9% under the room temperature of 20 ℃. With increasing the content of CNFs, the powder force decreases gradually, the covolume increases gradually, the burning rate decreases gradually, and the pressure exponent increases slightly. When the dosage of CNFs is 0.5%, the powder force, covolume and pressure exponent of high-energy TEGDN gun propellant are 1191.91 kJ·kg^-1, 0.870 L·kg^-1 and 1.06, respectively, compared with the reference sample, they have a reduce of 1.9%, an increase of 5.1% and an increase of 4.2%. respectively