The aging properties of polypropylene insulating materials in water treeing have become increasingly important due to their widespread use in power cables. In this study, accelerated aging experiments focusing on water treeing were conducted using the water needle electrode method. Isotactic polypropylene (iPP) and random copolymer polypropylene (PPR) were among the insulating materials investigated. The impact mechanism of crystalline differences on water tree growth properties was analyzed through a combination of techniques including polarizing optical microscopy (POM), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The results revealed distinct differences between iPP and PPR: iPP exhibited a dendritic water tree morphology with finer branches and larger water tree areas, while PPR displayed a denser morphology with thicker branches, and less pronounced length variation in the later stages of aging. While the spherulites in PPR are layered stacked structures with smaller overall sizes, similar to the β nucleating agent PP, contributing to its denser water tree morphology. Furthermore, the lamellar spherulitic structure hindered the penetration of water tree channels, thereby enhancing PPR's resistance to water treeing. This comparative analysis sheds light on the influence of crystalline structure on the water treeing behavior of polypropylene insulating materials, providing valuable insights for their application in power cable insulation systems.