[Objective] In order to elucidate the regulatory mechanism of the double petal trait in roses, we obtained an AG homologous gene RcAGL61 associated with flower development. [Method] qRT-PCR was used to analyze the expression patterns of RcAGL61 in the flower buds of double-petaled strain and single-petaled strain in Rosa chinensis ''Zhaiye Tengben Yuejihua'' × R. chinensis ''Old Blush'' population, and RcAGL61 was cloned from double-petaled lines and single-petal lines, and bioinformatics analysis, subcellular localization and VIGS experiments were carried out. [Result] The results showed that:(1) The expression level of RcAGL61 was significantly higher in the five developmental stages of flower of single-petaled strain than that of double-petaled strain, and the expression level was significantly higher in S4-S5 stages than in S1-S3 stages in single-petaled strain. (2) The coding sequence of RcAGL61 was consistent in double-petaled strain and single-petaled strain, with a length of 495 bp and a similarity to the RcAG coding sequence of 30.75%, encoding 164 amino acids, containing a MADS-Box conserved domain, belonging to the MADS-Box gene family. (3) RcAGL61 protein was subcellularly localized in the nucleus. (4) When the gene was silenced by VIGS technique in R. chinensis ''Old Blush'', the number of petalized stamens increased and the number of petals increased, while the number of stamens decreased. The number of sepals and pistil had no significant change. [Conclusion] RcAGL61 is involved in regulating the transition between stamen and petal primordium, and affecting the number of petal in roses.