Under the conditions of 16 h light/8 h dark,13 h light/11 h dark and 10 h light/14 h dark,the authors studied the effects of photoperiod on agronomic traits and photosynthetic characteristics of ensilage corn ‘Huanong 1’,at different nitrogen levels of N₁ (75 kg/hm²),N₂ (225 kg/hm²),N₃ (375 kg/hm²).The capacity of tolerating high nitrogen stress was analyzed.The results showed that:(1)the root length,root surface area and root volume were increased by 113.19%,45.73% and 97.71%,respectively,under 16 h light,compared with 10 h light.The contents of chlorophyll and net photosynthesis rate of leaves were higher by 97.90% and 60.24% under 16 h light.The leaf number under 16 h light was twelve more than that under 10 h light,with extremely significant difference.While photoperiod did not influence plant tiller number significantly.(2)Root diameter was decreased gradually with the extension of photoperiod.‘Huanong 1’ ensilage corn displayed the biological characteristics of resisting high nitrogen stress under 16 h light,and the indexes of root morphology and some agronomic traits were improved with increasing of nitrogen level,but the traits indexes declined gradually with the increasing of nitrogen level under 10 h light.(3)As the photoperiod extended gradually,aboveground biomass also increased significantly.Therefore,the authors believed that long photoperiod promoted the growth and development of photoperiod sensitive corn ‘Huanong 1’,and also enhanced the adaptation ability of it to high nitrogen.