Abstract: Taking grafted four-year-old walnut ‘Nonghe No.1’ as test material, the effects of ethephon on chlorophyll, osmotic regulation substances and photosynthetic products were studied by spraying ethephon on the leaves of walnut in autumn, in order to provide reference for effective prevention of cold frost in late autumn and early winter.The results showed that at the later stage of sampling, chlorophyll content of spraying 0.25 mg·L^-1 ethephon increased by 7.77%,but spraying 0.50 mg·L^-1 and 1.00 mg·L^-1ethephon significantly decreased by 9.56% and 35.84% compared with the control（P＜0.01）.However, the MDA content of spraying 0.50 mg·L^-1 and 1.00 mg·L^-1 ethephon was significantly increased by 17.40% and 51.83%,respectively（P＜0.01）.And the proline content of spraying 0.50 mg·L^-1 and 1.00 mg·L^-1 was significantly increased by 11.88% and 58.70%（P＜0.01）.Compared with the control, net photosynthetic rate（Pn） of spraying three treatments decreased by 10.19%,15.05% and 20.02%,respectively.The starch content significantly decreased by 10.43%,26.68% and 24.76%（P＜0.01）.Soluble sugar content was significantly reduced by 11.18%,15.79% and 20.60%（P＜0.01）.Therefore, ethephon sprayed at leaf aging stage can not only reduce chlorophyll content, Pn and accumulation of starch content, but also accelerate leaf senescence.It also reduced reducing sugar and soluble sugar contents, ethephon at 0.50 mg·L^-1 and 1.00 mg·L^-1 could increase MDA content and proline content of leaves, and leaves were defoliated 5 days and 13 days earlier than the control, respectively.