We used leaves of tree peony ‘Manyuan Chunguang’ as the materials to determine the contents of flavonol, anthocyanin, proanthocyanidin, chlorophyll, and carotenoid in different leaf color stages. RHSCC and Colorimeter were used to measure the leaf color phenotype; the expression level of flavonoid biosynthesis genes in different leaf color stages were detected by qRTPCR, and the relationships between pigments and flavonoid biosynthesis genes were analyzed. The potential causes of red faded in tree peony leaves were analyzed, and which provided genetic resources for further study on the molecular mechanism of this phenomenon. The results showed: (1) with the development of the tree peony leaves, the purplishred color was disappeared, the yellowgreen color was gradually appeared, and the adaxial (upper) and abaxial (lower) surface of leaves showed two different color changes. The RHSCC value, L^* and a^* values on the abaxial (lower) surface of leaves were higher than that of the adaxial (upper) surface, while the b^* and C^* values were lower than that of the adaxial (upper) surface.（2） The purplishred leaf was rich in anthocyanin and proanthocyanidin, while yellowgreen leaf was rich in chlorophyll, carotenoid and flavonol. (3) The expression levels of PsDFR and PsANS were consistent with the change trend of anthocyanin content, while the expression level of PsFLS and PsANR were consistent with the trend of flavonol content and proanthocyanidin content, respectively. (4) The expression pattern of PsMYB113 was significantly and positively correlated with the anthocyanin content, while the expression pattern of PsMYB4 was significantly and negatively correlated with the anthocyanin content；the expression pattern of PsMYBF1 was significantly and positively correlated with the flavonol content. The study found that leaf purplishred color faded was mainly caused by the decrease of anthocyanin content, and the decrease of anthocyanin content was the result of the coordinated expression of structure genes such as PsDFR, PsANS, PsFLS in the later developmental stages of tree peony leaves. In addition, PsMYB113, PsMYB4, PsMYBF1 may be the important transcription factors that regulated the above mentioned structure genes.