As an important link between plant and soil environment, fine roots can reflect the adaptability of plants to the living environment. Based on the functional traits of fine roots, exploration on mechanism of plants adaptive to environment would be significant for the vegetation restoration. In this study, 11 tree species in different stand sites of coastal saline-alkali land were selected, and six anatomical traits of 1-4 order fine roots were examined, including the fine root diameter, root cortex thickness, root stele diameter, the number of vessels, vessel diameter, and vessel density. At the same time, the soil physical and chemical properties in the forestlands where the fine roots of tree species are sampled were determined. The responses of fine root anatomical traits to soil environments were analyzed, and the study would provide a scientific basis for the vegetation restoration and plant community construct on coastal saline-alkali lands. The result showed that The fine root diameters of different orders were significantly different, and the fine root diameters increased with the increase of root order, while the fine root diameters of the same root order showed significant interspecific difference (P < 0.05). The root cortex thickness in 1-2 order fine roots and the vessel density in 3-4 order fine roots also showed significant differences among tree species (P < 0.05). Based on clustering of forest lands, the roots had larger cortex thickness of 1-2 order roots but less vessel density of 3-4 order roots in site 1 (the relatively higher salinization of soil) than those of other two sites. Furthermore, the root diameters and the stele diameters were more developed in site 1 (the relatively higher salinization of soil). The anatomical structure of the lower order roots of tree species was most closely related to the soil environment. The diameter of the first order roots was positively correlated with soil pH (P < 0.05), negatively correlated with soil nitrate nitrogen (P < 0.05). The redundant analysis (RDA) of soil properties and fine root anatomical traits showed the characteristic values were 0.640 and 0.196 in the two axes (RDA1 and RDA2), and soil available nutrient contents were positively related to RDA1 while the anatomical traits of lower order roots were negatively related to RDA2. The anatomical traits and soil pH value could explain more information of the tree species differentiation in saline-alkali soil environments, and the root diameter and the root cortex thickness in lower order fine roots demonstrated strong responses to soil saline-alkali environments, which would provide some references for the selection of tree species for the vegetation restoration in coastal saline-alkali environment in the future.