Fine roots play an important role in plant nutrient acquisition and ecosystem carbon allocation. Here we clarified the variation patterns of root traits based on root order or root functional modules, as well as the relationship between root traits and mycorrhizal colonization of different ectomycorrhizal tree species. This study determined the changes in branchingbased and functionbased root traits and ectomycorrhizal (ECM) colonization of six coexisting temperate tree species. The results showed that: (1) root diameter and individual root length increased, while specific root length and root branching intensity decreased from the first to fifth order roots. There were significant differences between studied tree species within the same root order for all root traits, especially two gymonsperms (Pinus tabuliformis and Larix gmelinii) had thicker root diameter than other four angiosperms. (2) Absorptive fine roots (AFR) and transport fine roots (TFR) both showed that, for a given tree species, all root traits existed significant differences; among tree species, root diameter, specific root length (SRL) and root tissue density existed significant differences, but individual root length and root branching intensity had no significant differences. (3) ECM colonization was the highest in Larix gmelinii and the lowest in Carpinus cordata and Betula platyphylla. Moreover, ECM colonization was significantly positively correlated with root tip diameter and negatively correlated with SRL. These results have shown that the variation patterns of branchingbased and functionbased root traits among species were not completely consistent. Individual root length and root branching intensity for AFR and TFR had no significant differences among tree species. Additionally, the coefficient of variation of specific root length and root branching intensity of AFR was larger than that of other root traits, indicating these two root traits are more sensitive to environmental changes. Tree species of basal clades tend to produce thicker root diameter and rely more on mycorrhizal fungi.