Abstract: The dynamic fracture toughness of the bionic spiral structured composite material was studied through three-point bending dynamic impact experiment and numerical simulation. The structure is a bionic composite structure based on the Bouligand structure design. Firstly, 8 groups of specimens with different angles were prepared by 3D printing technology using two kinds of substrates, soft and stiff, and the dynamic three-point bending impact tests were completed by using an improved split Hopkinson bar. The displacement-load curve, fracture time and fracture energy were obtained, and the final fracture morphology of the sample was analyzed. Then, the numerical simulation of the whole process of specimen fracture was completed in ABAQUS software, and the crack initiation and propagation process were analyzed. Both the experimental and numerical simulation results show that the helix angle has a great influence on the fracture toughness of the specimen, in the range of the helix angle of 0°-75°, the fracture toughness of the specimen increases with the increase of the angle, while when the helix angle is 90°, the fracture toughness of the sample drops sharply. In the process of experiment, it is observed that there is a crack deflection phenomenon during the dynamic fracture process of the sample. Finally, the influence mechanism of the crack deflection on the dynamic fracture was investigated. The results show that the crack deflection changes the local fracture mode of the composite material, increases the fracture area, and therefore improves the fracture toughness of the material.