Abstract: We aim to study the function of psy gene and its molecular mechanism in petal coloring. A psy gene was cloned from the Rhododendron molle cDNA by using RT-PCR and RACE methods. The full length of the psy gene was 1638 bp, named RmPSY (GenBank accession No. KX230461), which contained a 1296 bp open reading frame encoding 432 amino acid residues. RmPSY, a hydrophilic unstable protein with no signal peptide, was a non-secreted protein. The putative protein molecular weight was 48.91 kD and its theoretical isoelectric point was 8.78. Homologous alignment showed that it shared 81% amino acid identities with PSY from other plants in GenBank. The phylogenetic tree constructed on the basis of amino acid sequences of PSY suggested that the relationship between R. molle and Vitis vinifera was the most intimate. The results showed that the RmPSY gene was expressed in the petal during the flower development. The RmPSY transcripts were the most abundant in the initial opening period of flower, low in the bud stage, and decreased during the blooming period of flower. This study may provide references for further research on the molecular mechanism of RmPSY involved in the formation of R. molle flower color.