To investigate the fracture toughness of natural slate under dynamic loading, dynamic impact tests were conducted on notched semi-circular bending slate specimens by a 50 mm diameter split Hopkinson pressure bar testing system and the crack growth process was recorded by the high-speed cameras. Furthermore, the dynamic fracture toughness and crack propagation rate of slate under different impact pressure and prefabricated crack lengths were studied. The results show that the dynamic fracture toughness of the specimen is positively correlated with the impact pressure and loading rate, and the dynamic fracture toughness first increases and then decreases with the rise of the prefabricated crack length. According to the fitting results, the dynamic fracture toughness of the specimen reaches the maximum value when the prefab crack length is 7.45 mm. The maximum values of dynamic fracture toughness at 0.2, 0.3 and 0.4 MPa were 2.99, 3.57 and 4.14 GPa·m^1/2, respectively. The failure process of the specimen can be divided into five stages: dynamic damage, crack propagation, crack formation, crack propagation, and specimen fracture. The propagation speed of the main crack of the specimen greatly fluctuates, while the prefabricated crack length has little effect on the propagation velocity of the specimen. The study revealed the differences in dynamic fracture behavior of slate specimens under different working conditions.