To study Ptcor8 expression related to the defoliation of Poncirus trifoliate Raf. and the temperature, 2-year-old seedlings of 60 potted Poncirus trifoliata Raf. with similar diameter, in the temperature-controlled chamber（20~25 ℃）, were transferred to the field every 10 days from the 14th November, 2008 to January of next year, meanwhile, another 10 seedlings were put in the field as the control. The Poncirus seedlings in the temperature-controlled chamber and those transferred to the field after the 14th December were non-deciduous. However, those transferred to the field before the 14th December was deciduous, and their defoliating period delayed along with the time outside the temperature-controlled chamber. In the deciduous and the non-deciduous the expression of Ptcor8 gene was both detected. Furthermore, by qPCR, the more change of temperature and the longer duration of low temperature, the higher expression of Ptcor8. Therefore, the expression of Ptcor8 gene may not be directly related to the physiological defoliation of Poncirus trifoliate Raf., but rather closely related to low temperature induction.