Abstract: In order to clarify the transcription expression pattern and functions of β-carotene hydroxylase gene(β-OHase) in Nicotiana tabacum and further to regulate the metabolism of carotenoids in tobacco, the expression level of β-OHase in different tissues and organs of cv.Honghuadajinyuan(Nicotiana tabacum) at full flowering stage was studied by Real-time PCR.On account of the depression of β-OHase expression in Nicotiana benthamiana via the gene silencing system induced by tobacco rattle virus, the expression levels of downstream genes(such as VDE & ZE) were detected by Real-time PCR and the contents of carotenoids(β-carotene, violaxanthin and neoxanthin) in tobacco were determined after β-OHase silencing.The results showed that the expression level of β-OHase was significantly higher(P < 0.05) in leaves than in the other organs. Comparing with the control, the expression levels of VDE & ZE and the contents of violaxanthin and neoxanthin significantly decreased, while β-carotene content obviously increased(P < 0.05) after β-OHase silencing.