Abstract: Water conservation, as an important component of ecosystem services, is directly related to the resilience and sustainable development of the local economy, society, and ecosystem. In order to deeply explore the spatiotemporal evolution and driving mechanism of water conservation in tropical rainforest, taking Hainan Tropical Rainforest National Park as a pilot, this paper used ArcGIS and InVEST model to evaluate the data of five periods in 2000, 2005, 2010, 2015 and 2020, analyzed the temporal evolution and spatial distribution pattern of water conservation, and used LightGBM machine learning to explore the main driving factors of temporal and spatial changes of water conservation. The results showed that the water conservation service in Hainan Tropical Rainforest National Park fluctuated significantly on a time scale, showing a trend of first decreasing and then increasing from 2000 to 2020. The amount of water conservation in the five periods was 5.36×10⁹, 4.23×10⁹, 3.93×10⁹, 4.30×10⁹ and 4.34×10⁹ m³, respectively. In terms of spatial scale, the distribution pattern was significant different, characterized by ‘high in the east and low in the west, and high in the south and low in the north’. Water conservation had a strong spatial aggregation pattern (Moran′s I>0.93, Z>2.58), with more spatial cold spots in the western region and more hot spots in the eastern region. The honeycomb chart showed that precipitation, evaporation and land use and land cover (LULC) had higher marginal contribution to water conservation. Water conservation was positively correlated with precipitation and negatively correlated with evaporation, and was significantly affected by LULC. The results showed that the water conservation services exhibited obvious temporal evolution pattern and spatial variation pattern, and exhibited spatial agglomeration characteristics in Hainan Tropical Rainforest National Park. The dual effects of natural factors including precipitation and evaporation and human activities including LULC are the main driving factors of water conservation changes. This study provides a theoretical basis for the identification and planning of key areas for water conservation in Hainan Tropical Rainforest National Park, the maintenance of water conservation functions, and the decision-making management of national parks.