Abstract: In order to study the mechanism of the effect of natural fractures encountered of the shale fracture during hydraulic fracturing and understand the fracture mechanics characteristics of the rock mass, three-point bending specimens with semicircular disks at different angles from the pre-cutting were processed using natural fractured shale. The fracture propagation and failure characteristics of the semicircular shale were studied through the three-point bending test. The fracture toughness characteristics under different natural fracture angles and pre-cutting positions were obtained. The expansion pattern and turning rules of the fractures were analyzed based on the characteristics of acoustic emission. The research results reveal that: 1) Under the influence of bedding planes and natural fractures, prefabricated fracture paths exhibit “Z-shaped” trajectories. When the natural fracture inclination is low (0° and 30°) and high (90°), planar fractures are formed. When the natural fracture inclination is moderate (45° and 60°), non-planar fractures are formed. The actual incident angle is greater than the initially set natural fracture inclination, and during the fracture propagation process, the fractures shift towards the natural fractures. 2) Due to the influence of natural fractures, when the prefabricated fractures start to form, they do not align along the direction of the prefabricated fractures. The initiation angle and the direction of the prefabricated fractures have a certain angle difference. 3) As the intersection angle between prefabricated fractures and natural fractures increases, propagation transitions from “along natural fractures” to “directly crossing natural fractures”. Significant roughness contrast between prefabricated and natural fractures is observed. After the matrix breaks, the fracture surface has good self-supporting properties. The research results have certain guiding significance for optimizing the design of shale’s hydraulic fracturing, regulating the interference between the fractures and the natural weak planes of the reservoir, as well as the communication process.