Abstract: Tropical cloud forests harbor a rich diversity of Vascular Epiphytes, which play important roles in maintaining forest water cycles and biodiversity. Previous studies on vascular epiphytes have primarily focused on macro-environmental factors such as elevation and precipitation, whereas the effects of micro-scale light environments within forest canopies and their spatial heterogeneity on community diversity and assembly processes remain poorly understood. This knowledge gap is largely attributable to the difficulty of continuously characterizing the three-dimensional distribution of light under complex canopy structures using traditional methods. To investigate the effects of light availability on Vascular Epiphyte diversity, field surveys were conducted in 20 plots (20m×20m) within the tropical montane cloud forest of the Bawangling region in Hainan Tropical Rainforest National Park. Unmanned aerial vehicle (UAV)-borne LiDAR data were acquired to generate three-dimensional point clouds of forest canopies, quantify the three-dimensional understory light environment and its spatial heterogeneity via a radiative transfer model, and derive light environment metrics such as photosynthetically usable light flux. Relationships between different light environment metrics and the species composition and diversity of Vascular Epiphytes were then analyzed. The results revealed that different light environment metrics exhibited varying relationships with community diversity. Among them, the vertical light attenuation rate was significantly negatively correlated with species richness (r=−0.48, p<0.05). In addition, Vascular Epiphyte diversity at different height strata showed distinct responses to changes in light availability, indicating that the vertical distribution of Vascular Epiphytes is not driven solely by light maximization but is jointly regulated by multiple environmental factors. These findings suggest that canopy-derived vertical light structure and its spatial heterogeneity may play important roles in influencing Vascular Epiphyte community assembly. This study provides quantitative evidence for understanding diversity patterns of Vascular Epiphytes in tropical montane cloud forests from a three-dimensional light-environment perspective.