Based on the engineering background of the slope containing tension cracks at the western end slope of Shunxing Open-pit Coal Mine, a slope stability analysis model considering extreme rainfall infiltration was constructed by using seepage theory and flu-id-solid coupling numerical simulation methods. The evolution patterns of the stress field, displacement field, and safety factor under no rainfall and various rainfall intensities were systematically investigated. The influence mechanism of the development degree and spatial distribution characteristics of tension cracks on slope stability was revealed, and the coupling disaster-inducing effect of extreme rainfall and cracks was elucidated. It was found that slope stability was significantly reduced by the presence of cracks, and the greatest risk was posed by multiple cracks developing toward the slope face, which were prone to connection, thus forming potential slip surfaces. Under no rainfall conditions, the maximum displacement of cracks extending toward the slope face was observed to increase from 0.74 m to 1.13 m, exceeding the 1 m instability criterion. During extreme rainfall, cracks were observed to become preferential infiltration pathways for rainwater, leading to a sharp rise in pore water pressure and rapid ex-pansion of the deformation zone. At a rainfall intensity of 83.4 mm/h, localized deformation at the slope crest was found to exceed 1 m. The slope safety factor was reduced by the coupling effect of rainfall and cracks from 1.18 (without cracks) to 1.07 (with cracks), and was further decreased to 0.9 under extreme rainfall, representing a nearly 24% reduction, by which the risk of triggering overall instability was highly in-creased. When the rainfall intensity was set to 2000 mm/d and sustained for 1 hour, the maximum displacement at the slope crest was also found to exceed 2 m, indicating that the slope was nearing failure. Theoretical guidance and technical support for disaster prevention and mitigation during extreme rainstorms in open-pit mines located in arid and semi-arid regions can be provided by the research findings.