Abstract: The visualization and quantification of low-velocity impact damage are significant for improving the reliability and load-bearing efficiency of 3D braided composites. The 100 J low-velocity impact tests were carried out on 20° and 40° braided samples with a drop hammer impact instrument. Micro-CT was used to acquire images of the internal damage based on a threshold-based automatic extraction method. Afterwards, the damage was divided into 8 parts along two directions to obtain the data of front pit depth, back bulge height, damage extension length, damage area and volume of each section. The results show that the main damages, such as fiber damage, matrix crack and interfacial debonding spread around the impact center symmetrically. Meanwhile, the damage of the 20°sample is more serious than that of the 40°sample, and the damage expansion is larger along the axial yarn direction. Among them, the axial damage extension length and damage stacking area of the 20°sample can reach 50.481 mm and 437.039 mm², respectively, which are far greater than the corresponding lateral values of 23.582 mm and 104.004 mm².