Abstract: As an important auxin efflux carrier family in plants,PIN protein family shows extensive physiological effects in plant growth and development.In order to further understand the function of Bp PIN3 and explore its response to different hormone signals and abiotic stresses during Betula platyphylla development,the Bp PIN3 promoter sequence was analyzed by bioinformatics methods.Tissue expression patterns of roots,stems,leaves and apical buds of annual and biennial B.platyphylla clones were analyzed respectively.The seedlings were used as conduct hormone induction and light stress treatment with 100μmol·L^-1auxin（IAA）,100μmol·L^-1gibberellin（GA₃）,200μmol·L^-1abscisic acid（ABA）and long light conditions,respectively.RNA was extracted from leaves and roots of B.platyphylla at 0,2,4,8,16,24 and 48 h after hormone treatment and at0,1,3,6,12,24,48 and 72 h after light stress,and q RT-PCR was used to analyze the expression of Bp PIN3.The results showed that the Bp PIN3 promoter sequence contained different types of auxin response elements such as gibberellin,abscisic acid,and methyl jasmonate,as well as multiple stress-related cisregulatory elements.Bp PIN3 was expressed in many tissues of birch in different growth years,especially in leaves,and the expression of Bp PIN3 in the second year was higher than that in the first year.The relative expression of Bp PIN3 gene was different in different parts under different treatment conditions.IAA and GA₃could induce the up-regulation of Bp PIN3 expression in leaf.Under ABA treatment,except for 16 and 48 h,the expression pattern of Bp PIN3 gene was opposite to that under IAA treatment.IAA,GA₃and ABA could induce the expression of Bp PIN3 in root,but shading stress induced the expression of Bp PIN3 gene in leaf,the relative expression of Bp PIN3 gene was significantly higher than that of the control（0 h）from 12 h in root,IAA,GA₃and ABA could induce the expression of Bp PIN3 in root,shading stress induced the expression of Bp PIN3 gene in leaf;the relative expression of Bp PIN3 gene was significantly higher than that of the control （0 h）from 12 h in root.The results suggested that Bp PIN3 gene played the important regulatory role in the growth and development of B.platyphylla,and the signal transduction pathways of IAA,GA₃and ABA and plant light response.