The Han Dynasty ancient bridge site at Sandian Village in Xi’an is the only known Han Dynasty wooden bridge discovered archaeologically in the Chan River Basin. To understand the deterioration of its wooden components, preliminary analyses were conducted on wood species and preservation status after excavation using methods such as tree species identification, moisture monitoring, infrared spectrometry, X-ray diffraction, and differential thermal analysis. The results indicated that the wooden piles were from tree species belonging to the Pinaceae spruce genus, Pinaceae hemlock genus, and Meliaceae Toona. After excavation, cracks, discoloration, and other forms of deterioration appeared. The severity of these issues varied among species:spruce showed thinner cracks; hemlock had more numerous cracks; and Toona sinensis exhibited wider cracks and flaking. Toona also showed the greatest degree of color change. The chemical compositions of the three wood species had all undergone change, with varying degrees of degradation in cellulose, hemicellulose, and lignin. Spruce had the mildest degradation, while Toona sinensis had the most severe. These findings provide foundational data for the conservation of the wood from this ancient bridge site and serve as a reference for future studies of similarly excavated archaeological wood.