Phytoremediation exerts enormous function on the remediation of heavy metals. Excavation and authentication of pivotal genes connected with Cd accumulation and tolerance is prerequisite for gene engineering enhanced plants for cadmium phytoremediation. In the present study, PtrAREB3, ABA Responsive Element Binding protein, was identified from the Populus trichocarpa. PtrAREB3 was principally expressed in the leaves and was markedly induced during ABA and Cd stress. PtrAREB3 acts in the nucleus and specifically bind to ABA Responsive Element (ABRE) in the promoters of target genes. Under cadmium stress, poplar PtrAREB3 will be activated, and the PtrAREB3 directly regulates target genes (SDI1, CAX3, ABCG25, ABA2, Peroxidase, and HUP32) expression by combining the CACGT motif of its promoter. Moreover, activated target genes can increase the tolerance of plants to cadmium stress by reducing the production of oxides, reducing chlorophyll degradation, and increasing the synthesis of proline and activating the antioxidant system. Furthermore, PtrAREB3 may regulate the expression of genes (ZIP2, CCH1.1, NRAMP1, ABCC1 and MTP1) related to Cd uptake, transport and detoxification, thus increasing the accumulation of cadmium in plants. Overall, overexpressing PtrAREB3 in poplar enhanced cadmium accumulation and cadmium tolerance through direct or indirect regulation of downstream gene transcription.