The hydrodynamic software FLUENT was used to study the drag coefficient of fragments with different initial velocities （≤2500 m·s^-1） and altitudes （≤20 km）， and the velocity attenuation model of fragments with different altitudes was corrected Then the accuracy of the corrected model was verified by the corresponding velocity attenuation characteristic tests with low atmospheric pressures. The results show that the calculated results of spherical fragments with an initial velocity of 700 m·s^-1 and cuboid fragments with an initial velocity of 1000 m·s^-1 using the corrected velocity attenuation model are in good agreement with the experimental results that the errors are less than 5%， and the calculation accuracy of the modified velocity attenuation model is about 10% higher than that of the original model. The corrected velocity attenuation model of fragments can be used to calculate the influence of the drag coefficient， which is varied with the altitude， on the velocity attenuation coefficient of fragments， to improve the calculation accuracy of the fragment velocity， and to further improve the accuracy of the power evaluation of the fragment warhead.