Abstract: Using the cDNA from the leaves of fingered citron‘Qingpi’as the template，the full cDNA of ERF（ethylene response factor）gene（1 160 bp）was cloned by reverse transcription polymerse chain reaction（RT-PCR）and rapid-amplification of cDNA ends（RACE）. The gene was named CmsERF6，containing an open reading frame（999 bp）and encoding a protein of 333 amino acids. The expression of ERF6 was determined by real-time quantitative PCR in the leaves of fingered citron‘Qingpi’and trifoliate orange. The results showed that ERF6 was expressed in both fingered citron‘Qingpi’and trifoliate orange，but the trend of expression was apparent difference. Especially in the trifoliate orange，the expression of ERF6 was increased by about 4 000 times than the control group. The same trend was found in changes of relative electric conductivity and gene expression of ERF6，which indicated that ERF6 may be involved in cold stress response pathway and may play an important role in cold tolerance.

Key words: fingered citron, trifoliate orange, cold stress, ERF6