Abstract: 【Objective】Explore the tissue specificity of the cytochrome P450 genes in the triterpenoids from birch(Betula platyphylla Suk.)and expression pattern under treatments of methyl jasmonate(MeJA), salicylic acid(SA), gibberellin(GA₃), abscisic acid(ABA), ethephon and leaf injury.【Method】Three BpCYP450 genes were screened from the transcriptome of B. platyphylla Suk. and named BpCYP4, BpCYP5 and BpCYP14, respectively. The molecular structure of BpCYP450 proteins and relationship with CYP450 proteins of other species of plants were described by bioinformatics analysis. The tissue specificity of BpCYP450 and the expression characteristics under hormone and injury were analyzed by QRT-PCR.【Result】Bioinformatics results showed that the size of BpCYP4, BpCYP5 and BpCYP14 were 1 569, 1 584 and 1 530 bp, respectively, and contained the complete ORF, encoding 522, 527 and 509 amino acids, which were hydrophilic transmembrane proteins and mainly located in the chloroplast. Three BpCYP450 were closely related to leguminous plant CYP450 proteins such as Lotus japonicus, Lens culinaris and Pisum sativum. The ana-lysis of tissue-specific showed that BpCYP450s expression were higher in leaves and in roots,and lower in stems. The results of hormone and injury induction showed that BpCYP450 genes was induced by MeJA, SA, GA₃ and ABA, ethephon and injury. 【Conclusion】Three BpCYP450 are new members of the CYP450 genes family, with expression of tissue-specific and hormone induction. These results suggested that three CYP450 genes may play an important role in the growth and development the defense stress and the metabolites synthesis of birch.