The (GAI\RGA\SCL) gene family encodes plant-specific transcription factors that play crucial roles in plant growth and development, stress tolerance, and hormone network regulation. Plant dwarfing symptom is mainly regulated by DELLA proteins of the gene subfamily. In this study, the association between the gene family and Paulownia witches' broom (PaWB) was investigated. A total of 79 genes were identified using bioinformatics methods and categorized into 11 groups based on amino acid sequences. Tandem duplication and fragment duplication were found to be the main modes of amplification of the gene family. Gene structure analysis showed that more than 72.1% of the had no introns. The genes also contained unique DELLA structural domains; only , which showed significant response to PaWB phytoplasma infection in stems, showed significant tissue specificity and responded to gibberellin (GA3) in PaWB-infected plants. We found that the internodes were significantly elongated under 100 µmol·L GA3 treatment for 30 days. The subcellular localization analysis indicated that is located in the nucleus and cell membrane. Yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays confirmed that PfGRAS12 interacted with PfJAZ3 in the nucleus. Our results will lay a foundation for further research on the functions of the gene family and for genetic improvement and breeding of PaWB-resistant trees.