【Objective】 Paeonia×suffruticosa (peony) is a traditional ornamental flower. Because its short flowering period greatly limits the ornamental value of peony, the PoERF4 gene of ostii ‘Feng Dan’ was cloned to study its sequence and expression characteristics in different flowering periods, tissues, varieties and hormone treatments. This study aimed to provide a theoretical reference for further research on the regulation of PoERF4 during the flowering, growth and development of tree peony. 【Method】 Using ‘Feng Dan’ as the material, based on the results of the three-generation full-length transcriptome sequencing of ‘Feng Dan’, the sequences with high homology were screened, the PoERF4 gene was cloned by RT-PCR technology, and bioinformatics and expression pattern analysis were performed. 【Result】The open read frame (ORF) of the PoERF4 gene was 747 bp, which encoded 248 amino acids. The molecular formula of PoERF4 was C_{2 217}H_{3 689}N₇₄₇O₉₃₃S₁₇₄, which is a hydrophilic protein containing a conserved AP2 superfamily domain with no transmembrane structure. The secondary structure contained 28 amino acids in the α-helix, 48 amino acids in the extended chain, and six amino acids in the β-turn. Fluorescence quantitative analysis found that the PoERF4 gene was mainly expressed in the petals of the half-opening period of ‘Feng Dan’ and it was expressed in different tissues of ‘Feng Dan’ peony, but its expression was highest in the leaves, followed by in the petals and roots. The expression level was the highest in the late-flower cultivar ‘Lianhe’. Under auxin treatment, the PoERF4 gene could respond. 【Conclusion】The PoERF4 gene was successfully isolated from ‘Feng Dan’ and it was speculated that it plays an important regulatory role in the development of flowers and leaves and is involved in the auxin signal transduction process of ‘Feng Dan’.