Abstract: In order to screen for the resistance genes of trees and cultivate transgenic trees with high resistance, Shanxin Poplar（Populus davidiana × P. alba var. pyramidlis） was used as the test material, and the 1 560 bp cDNA of the PdPapGH12（Potri.004 G109200.1） gene was cloned by RT-PCR. Bioinformatics analysis showed that PdPapGH12 encoded a protein of 519 amino acids, and the PdPapGH12 protein was a hydrophilic acidic protein. According to the prediction results of the subcellular localization of PdPapGH12, it might play a role in the hydrolysis reactions in the cytoplast. Protein structure analysis showed that PdPapGH12 shared high similarity with nine other GHs of four poplar varieties. RT-qPCR analysis showed that PdPapGH12 was relatively highly expressed in the stem base, old leaves and roots. Salt（NaCl, 200 mmol/L）, alkali（Na₂CO₃ solution, pH=10） and PEG 6000（Polyethylene glycol 6000; 30%） treatments for 48 hours could induce the up-regulation of PdPapGH12 in the apex, mature leaf and root. PdPapGH12 expression in the apex was down-regulated by the inducing of five plant pathogenic fungi for 48 hours. Only Sclerotinia sclerotiorum induction significantly upregulated the expression of PdPapGH12 in mature leaves. Fusarium oxysporum, Alternaria alternate and Rhizoctonia solani induction significantly increased PdPapGH12 expression in the roots. After 48 hours of phytohormone induction, ABA（100 μmol/L） only upregulated PdPapGH12 expression in the roots. SA（100 μmol/L） only upregulated PdPapGH12 expression in mature leaves, while JA（100 μmol/L） upregulated PdPapGH12 expression in both the mature leaves and roots. This study demonstrated that PdPapGH12 had a role in poplar’s resistance against environmental stresses and responses to phytohormone induction.