Abstract: To evaluate the impact of street tree structural characteristics on pedestrian thermal comfort in shallow street canyons in Fuzhou,this study measured tree height(TH),branch height(BH),crown diameter(CD) and leaf area density(LAD) from 159 street trees across 50 species in the city’s main urban area.Based on these 50 street tree species,54 virtual tree models were developed.By integrating ENVI-met simulations with Physiological Equivalent Temperature(PET)evaluation,the spatiotemporal mechanisms of their influence were analyzed,and suitable tree species for each orientation were identified.Results show that during periods of building shade,the thermal comfort performance of street trees in shaded areas was lower than in sun-exposed zones.Under the interactive effects of the four indicators,tree height and crown diameter were the primary factors enhancing thermal comfort,while leaf area density had a positive but slightly weaker influence.In contrast,higher branch height correlated negatively with thermal comfort improvements.Cluster analysis and screening indicated that optimal tree species differ by street orientation.Species such as Ficus benjamina,Ficus altissima,Acacia confusa and Delonix regia performed well across all orientations.Liquidambar formosana,Ficus concinna and Handroanthus chrysanthus notably improved thermal comfort in east- west streets,while Erythrina variegata excelled in north-south streets.Therefore,selecting tree species with relatively suitable structural characteristics for planting in street spaces of different orientations can effectively improve pedestrian thermal comfort.