In order to study the three-dimensional propagation of fractures under different initiation modes, a true triaxial experimental system is used to perform directional fracturing and borehole fracturing tests.The results show that the crack starts from the tip of the prefabricated crack and turns in the direction of the intermediate principal stress.The crack presents a double-wing bending shape and is still parallel to the direction of the maximum principal stress as a whole.In the borehole fracturing test, the fracture initiation is at the axial symmetric position of the borehole, the fracture propagation tends to be perpendicular to the minimum principal stress, and the crack is elliptical and self-similar.There are two typical stages of fracture propagation:pressure-cumulative and pressure stabilization stage.During the pressure-cumulative stage, the pump pressure rises sharply before reaching the initiation pressure.Acoustic emission energy surges and fluctuates sharply.During the pressure stabilization stage, the pump pressure curve develops in a zigzag pattern and tends to be stable.Acoustic emission energy levels are relatively low in this stage.The research can provide a reference for the fracturing of the hard roof in the coal mine.