Flower color and color patterns are important traits for ornamental species; for this reason, a comprehensive understanding of the genetic mechanisms underlying these characters is extremely significant for plant breeders. The tulip tree (Liriodendron tulipifera Linn.) is well known for its flowers, odd leaves and tree form. However, the genetic mechanism underlying its flower color remains unknown. In this study, a putative LtuPTOX gene was identified based on multiple databases of differential transcript expression at various developmental stages and the complete genome sequence of Liriodendron. Then, the full-length cDNA of LtuPTOX was derived from tepals and leaves using RACE approaches. Furthermore, the gene structure and a phylogenetic analysis of PTOX as well as AOXs, highly similar homologs in the AOX family, were used to distinguish between the two subfamilies of genes. In addition, transient transformation and qPCR methods were used to determine the subcellular localization and tissue expression pattern of the LtuPTOX gene. Moreover, the expression of LtuPTOX as well as pigment contents was investigated to illustrate the function of this gene during the formation of orange bands on petals. The results showed that the LtuPTOX gene encodes a 358-aa protein that contains a complete AOX domain (PF01768.17). Accordingly, Liriodendron PTOX and AOX genes were identified as only paralogs since they were rather similar in the sequence. LtuPTOX showed chloroplast localization, and expressed in the colored organs such as petals and leaves. In addition, increasing pattern of LtuPTOX transcripts lead to carotenoids accumulation on the orange-band in the development period of flower bud. Taken together, our results provide that LtuPTOX is involved in petal carotenoid metabolism and orange band formation in L. tulipifera. Meanwhile, the identification of this potentially involved gene will lay a foundation for further uncovering the mechanism of flower color formation in L. tulipifera.