Aiming at the method of mining coalbed methane by fracturing with guide groove, the theoretical analysis and numerical simulation method are used to analyze the change law of coal mechanical properties and the crack propagation mechanism after the jet fracture forms the fracture. The results show that there is a failure zone near the center of the jet-forming gap, and there are stress concentration areas on both sides of the gap. There is a more obvious plastic zone at the tip of the crevice, and its shape is a typical ear-like plastic zone. The crack initiation position is more conventional, it is determined by the difference between the stress in the direction parallel to the length of the crack and the direction parallel to the width of the crack; the direction of crack extension depends on the crack initiation position. The comparative analysis shows that it is more reasonable to use elastic–plastic fracture mechanics to calculate the initiation pressure with the crack starts from the tip, and the critical J integral model for the initiation of the crack tip is obtained. The initiation position of guided fracturing is more regular than conventional fracturing, and the initiation pressure of guided fracturing fractures is less than that of conventional fracturing under any stress combination.