Undergrowth shrub is an important component of subtropical evergreen broad-leaved forest, but the variation of fine root functional traits and the underground ecological strategy of undergrowth shrubs are still unclear. In this study, the characteristics of fine root diameter, root length, specific root length, tissue density, carbon concentration and nitrogen concentration of nine shrubs in Wanmulin Nature Reserve of Jian 'ou, Fujian Province were studied. We analyzed the variation of the functional trait of fine roots in root orders, the difference between the root traits of evergreen and deciduous shrubs, and the correlation between the morphology and chemical characters of fine roots in different root orders. Then we used principal component analysis to explore the variation dimension of fine root functional traits. The results showed that tree species and orders had significant effects on the morphology and chemical properties of the fine roots of the nine shrubs. The root diameter, root length and tissue density increased gradually with the increase of the root order, the specific root length and nitrogen concentration decreased gradually. There is no consistent pattern of change in carbon concentration. The fine root diameter, root length and nitrogen concentration of the first order root of deciduous shrubs were higher than that of evergreen shrubs, and the carbon concentration and tissue density were lower than that of evergreen shrubs, indicating that deciduous shrubs were more inclined to resource acquisition strategy than evergreen shrubs, while evergreen shrubs were more inclined to conservative strategy. In this study, there was a strong correlation between root diameter, specific root length and tissue density. The relationship of nitrogen concentration and tissue density of fine root was also strong. The relationships between other characters of fine root were not close or differed between root orders. The principal component analysis results showed that the variation of shrub root traits varies along a principal component axis, which represents the trade-off between resource acquisition and conservation strategy of shrub roots.