【Objective】This study aimed to explore the role of the auxin transporter PIN1 in plant growth and development in Liriodendron chinense.【Method】Three PIN1 homologous proteins were identified in the Liriodendron genome using bioinformatic methods, and expression pattern analyses of the three LcPIN1s genes were performed in different tissues and response to various abiotic stresses. An overexpression vector driven by the CaMV35S promoter was then constructed and transformed into Arabidopsis and Liriodendron×sinoamericanum, followed by phenotypic determination of growth and developmental traits in the transgenic positive lines.【Result】Three PIN1 homologous proteins were identified in the Liriodendron genome, named LcPIN1a, LcPIN1b and LcPIN1c. Expression pattern analyses showed that LcPIN1a was mainly expressed in leaves, while LcPIN1b and LcPIN1c were primarily expressed in roots and stems and stigmas when the plantlets transitioned into reproductive growth. In addition, all three LcPIN1 genes transcriptionally responded to drought stress, with LcPIN1b and LcPIN1c showing dependence on the biosynthesis of endogenous ABA, while LcPIN1a does not. Root length and plant height were significantly reduced in LcPIN1a-heterologous overexpression (LcPIN1a-HO) lines compared to wild-type Arabidopsis. The number of stamens was predominantly five in LcPIN1a-HO lines, whereas wild-type Arabidopsis typically contained six stamens. The regeneration of plantlets in LcPIN1a-overexpressing (LcPIN1a-OE) Liriodendron×sinoamericanum was significantly reduced compared to wild-type plants. In addition, the root length and plant height of LcPIN1a-OE regenerated seedlings were significantly lower than those of the wild type. The root structure of LcPIN1a-OE plants was significantly changed, with the taproot being less distinct.【Conclusion】The PIN1 proteins of L. chinense play a crucial role in vegetative and reproductive growth. Overexpression of LcPIN1 genes can be detrimental to normal plant growth and development.