Exploring the distribution of landscape ecological risks caused by land use changes is crucial for the ecological health of tropical rainforests, as well as for the protection of the authenticity and integrity of natural ecosystems. Based on land use data of National Park of Hainan Tropical Rainforest from 1980 to 2023, this article explores the optimal scale and spatiotemporal characteristics of landscape ecological risk assessment in the national park. The results show that: (1) 2.5 km is the optimal scale for landscape ecological risk assessment, as the response curve of the assessment unit gradient shows that both Shannon's evenness index and landscape separation index exhibit inflection points at 2.5 km. (2) Land use in the national park is relatively stable, with forest-grassland being the main conversion type that alternates frequently, while the inflow and outflow areas remain relatively balanced. The Moran's I of landscape ecological risk ranged from 0.3079 to 0.3600, and the spatial correlation shows an upward trend, demonstrating fluctuating moderate positive clustering. (3) Landscape ecological risk values fluctuate between 0.0241 and 0.0243, indicating a stable long-term trend. Risk zones exhibit steady development, forming a pattern of higher risk in the east and west, with lower risk in the center, and fragmentation along water bodies and roads. Conversions from higher risk levels to lower risk levels exceeded the reverse by 0.86%. High- and low-risk zones fluctuated and increased by 79.95 km2 and 103.63 km2, respectively. The lower-risk zone represents the largest proportion, averaging about 8.08% higher than other levels. High- and higher-risk zones cluster around areas with frequent human activities, such as water bodies and roads, while medium-risk areas are widely distributed in the southern part of the national park. The farther from water bodies and roads, the lower the risk level. Fluctuating risk level areas are distributed in strips along the edges of areas with the same level. In order to promote coordinated development with the natural environment, it is suggested to implement graded management and protection, establish a long-term monitoring mechanism for high-risk areas, optimize land use, reduce the planting and cutting of economic forest, and decrease landscape separation and fragmentation.