Abstract: Understanding its root system distribution and biomass estimation are crucial for elucidating the belowground ecological processes of tropical rainforest vegetation. As a keystone species of China's tropical rainforests, Parashorea chinensis plays a vital role in the emergent canopy layer. This study investigated the root system of a naturally uprooted P. chinensis. By using laser radar, we reconstructed the three-dimensional root architecture and restored its spatial distribution in situ. By integrating measured data on root diameter and length, we characterized its morphological structure and spatial arrangement. Based on allometric theory, we developed a root biomass estimation model using root diameter as the sole predictor, which achieved high predictive accuracy (R² = 0.98) for individual root biomass. Our results indicate that the root system of P. chinensis is primarily concentrated in shallow soil layers, providing mechanical stability for aboveground growth. Quantitative assessment shows coarse roots (diameter > 5 mm) dominate the root system (74% of total roots). Root diameter decreased exponentially with length, and allometric analysis revealed a significant relationship between root biomass and diameter (p < 0.01). This study provides a solution for visualizing the root system and quantifying the root biomass.