Abstract: As core technology for controlling blasting damage and ensuring slope integrity in open-pit mine slope excavation, presplit blasting effectively improves slope blasting quality, with parameter optimization playing a decisive role in engineering efficiency. To address prominent issues such as poor connectivity of presplit fractures and over-excavation of slope surfaces in open-pit mine slope blasting, this study adopts a combined approach of numerical simulation and field experiments based on an open-pit mine slope blasting project. The research investigates the influence of presplit hole spacing on blasting outcomes. Based on ANSYS/LS-DYNA finite element software, a 3D slope blasting model is established with presplit hole depth of 10 m, hole diameter of 150 mm, and hole spacing set at four working conditions （1.0 m, 1.3 m, 1.5 m, and 1.7 m）. The study investigates the stress evolution at boreholes and crack propagation patterns in rock masses post-blasting. The results demonstrate that presplit hole spacing significantly affects stress wave superposition effects and crack coalescence patterns. Notably, smaller hole spacing leads to excessive damage in inter-hole rock masses and generates large-scale damage zones at both the bench crest and toe. As the spacing increases, blasting-induced effects on inter-hole rock diminish, resulting in reduced stress superposition intensity and compromised presplit fracture connectivity, ultimately failing to form an effectively coalesced fracture surface. Among the tested spacings, the 1.5 m hole spacing configuration achieves optimal fracture connectivity with complete morphological integrity. Field validation trials adopting the 1.5 m spacing are conducted, including half-hole retention rate statistics through on-site fragment counting and slope flatness analysis using Hovermap 3D laser scanning technology. Results indicate: average half-hole retention rate reaches 92.1%, over 90% of slope surface points exhibit undulation spacing within ±0.1 m. These findings demonstrate superior field applicability, providing valuable references for similar slope blasting engineering projects.