In order to determine the optimal pre-splitting blasting parameter combination to ensure the safety and stability of a rock slope, a numerical simulation method was employed. Using the ANSYS/LS-DYNA software, a three-hole blasting model of the rock was constructed based on a Arbitrary Lagrange Eulerian algorithm. The accuracy of the model was verified through empirical formulas. On this basis, simulations of the pre-split crack process under different blasting parameter conditions were conducted, exploring the crack propagation patterns in the three-hole blasting of rock. A calculation and analysis of the blasting effects of the pre-split cracks was carried out, and the most effective decoupling coefficient and hole spacing parameters were selected. The research results show that as the decoupling coefficient increases from 1.00 to 3.00, the impact pressure on the hole wall significantly decreases. When the decoupling coefficient is 2.8, the impact pressure is close to the compressive strength of the rock. As the hole spacing increases from 70 cm to 110 cm, the tensile stress at the midpoint between the holes increases from 3.1 MPa to 9.8 MPa. However, when the hole spacing increases to 120 cm, the tensile stress decreases. At a hole spacing of 110 cm, the tensile stress between the holes reaches its maximum value. Based on these findings, the optimal decoupling coefficient is 2.8, and the optimal hole spacing is 110 cm. The results provide a reference for designing pre-splitting blasting parameters for rock slopes in the field and are of great significance for achieving precise blasting control and ensuring the safety and stability of rock slopes.