Abstract [Objective] As a precious peony breeding material, Paeonia delavayi has abundant flower color resources. Studying the regulatory effect of its MYB transcription factors on flower color can provide assistance for molecular breeding of peony flower color. [Methods] Using the flower tissue of yellow and red P.delavayi as materials, observing the distribution characteristics of anthocyanins in its cells through hand sectioning. Based on the transcriptome data of the two materials, a MYB transcription factor PdMYB57 was obtained through sequence alignment. The physicochemical properties and functions of the PdMYB57 transcription factor were predicted through gene cloning, bioinformatics analysis, phylogenetic tree, and homologous sequence alignment. Subsequently, Quantitative reverse transcription polymerase chain reaction (qPCR), transient expression in tobacco, and High performance liquid chromatography (HPLC) were used to validate the function of PdMYB57. [Results] The PdMYB57 gene has a complete open reading frame of 798 bp, encoding 265 amino acids, and is located in the nucleus as a hydrophilic unstable protein; Cluster together with the SG6 subfamily in the R2R3MYB family of Arabidopsis, as well as MYB transcription factors that promote anthocyanin synthesis in P.qiui PqMYB113,P.suffruticosa PsMYB57/PsMYB58 and Vitis vinifera VvMYBA1/VvMYBA2, and exhibit a typical R2R3 conserved domain [R/K] Px [P/A/R] xx [F/Y] motif; the qPCR results showed that the PdMYB57 gene has high expression levels in the sepals of red P. delavayi and leaves of yellow P. delavayi. In other tissues, the expression level is extremely low and almost non-existent, which is consistent with the transcriptome data results; HPLC detection showed that the tobacco leaves with transient expression of the PdMYB57 gene contain Cyanidin- 3-O-rutinoside (Cy3R) , while the tobacco leaves with CK control did not produce color and Cy3R was not detected in the extraction solution. [Conclusion] The PdMYB57 gene encodes an R2R3-MYB transcription factor, located in the nucleus as a hydrophilic unstable protein. Its expression is tissue-specific and promotes the synthesis of anthocyanins in plants.