To further understand the fracture damage process of complex fractures, this paper uses PFC2D software to conduct numerical tests on rock masses with different number of fractures based on the fracture mechanics theory, and analyses the influence of fracture dip angle, surrounding pressure and other factors on the strength and fracture expansion of rock masses. The study shows that the peak stress and initiation stress of single fracture decrease and then increase as the fracture inclination angle increases, and the peak stress increases from 120 MPa to 160 MPa when the surrounding pressure increases from 2 MPa to 8 MPa. In cases of 60° and 90°, the fracture inclination is mainly coplanar secondary fractures, and the peak stress of multiple fractures decreases significantly with the increase of the number of prefabricated fractures at different surrounding pressures. The research results can provide reference for further exploration of the destabilization damage law of fractured rock masses.