Abstract: In present study, we successfully isolated a gene from NRT2 family named PtNRT2.7. Bioinformatic analyses showed that PtNRT2.7 had 11 transmembrane regions, and hydrophobic regions and hydrophilic regions are distributed alternately on cell membrane without signal peptide. Subcellular localization analysis showed that the PtNRT2.7-GFP fusion protein is distributed on cell membrane. According to above findings, it belongs to a membrane protein. The expression features of Populus trichocarpa showed that PtNRT2.7 expresses in leaves, with the highest expression in mature leaves; the highest expression appears at 1 h under the nitrate stress; under the stress of SA/JA/GA/IAA, the expression of PtNRT2.7 is up-regulated in both above- and underground parts; under the stress of Eth/ABA/NaCl, the expression of PtNRT2.7 is down-regulated. The expression vector was constructed and transformed into Arabidopsis thaliana wild type (Col-0) and atnrt2.7 mutant using floral dip method. The stress of different concentrations of KNO3 showed that, when the concentration of KNO3 is more than 0.1 mmol/L, the root enlongation of overexpression lines is longer than others; the mutant lines are inhibited when the concentration is more than 1 mmol/L but the complementary lines can remove the inhibition. The result showed that hormones and NO-3 can induce PtNRT2.7, enhance the root growth and promote the absorption of nitrogen.