Abstract: Taking Songzao Mining Area as an example, RFPA software was used to simulate and analyze the propagation laws of hydraulic cracks under different conditions of different slot lengths and angles between different slots and ground stress component in the coal seams. The research shows that the pre-fitting slot can effectively reduce the cracking pressure and the fracture stability expansion pressure of the coal seam hydraulic fracturing near the borehole. Besides, it can also increase the crack extension range, even 2 times of the conventional drilling hydraulic fracturing.