Abstract: National parks are recognized as crucial for safeguarding regional hydrological regulation services, and the planted forests within their watersheds serve as important regulatory components for hydrological regulation functions. However, a key challenge facing national park management is how to enhance watershed hydrological regulation services by identifying spatial priority areas for the natural restoration of planted forests. The upper reaches of the Nandu River watershed in Hainan Tropical Rainforest National Park were selected as the study area. This region contains extensive rubber plantations. Through the Soil and Water Assessment Tool (SWAT) model, the impacts of rubber plantations on water yield, sediment yield, and total phosphorus output were analyzed, and priority areas for the natural restoration of rubber plantations were delineated. The results indicate that the natural restoration of rubber plantations has no significant effect on regional water yield, but reduces the annual total sediment yield by 77.44% and the total phosphorus output during the rainy season by 37.10%. The rubber plantations can be classified into four restoration priority zones, with the first\|priority restoration area accounting for 14.26% of the total rubber plantation area in the region. After restoration, the regional annual sediment yield can be reduced by 2.94 tons/hm², and the total phosphorus output can be decreased by 0.038 kg/hm². This study clarifies the hydrological regulation service benefits and spatial importance of rubber plantations, providing a theoretical basis and practical reference for ecological restoration of rubber plantations and the enhancement of hydrological regulation services in the study area.