Abstract:The regulation of adding nitrogen on crop physiological properties and yield after waterlogging stress can provide valuable information for restoring crop growth. In this study, the method of combining field and pot experiments were adopted, including four adding nitrogen rates of 0, 30, 60 and 90 kg/hm2 and three waterlogging time treatments of 0, 6 and 9 days. The results showed that compared with the treatment of only waterlogging stress but no adding nitrogen, adding nitrogen improved the physiological indexes and enhanced the yield, all the indexes had similar changing characters in both pot and field experiments. After 20 days from adding nitrogen, the chlorophyll contents in leaves, the activities of SOD, CAT and POD in leaves and roots, as well as the yield increased and the MDA contents in leaves and roots decreased while the waterlogging time decreased and the nitrogen rates increased, waterlogging time and nitrogen rates had significant interaction effects on the other physiological indexes and yield except the CAT activities in roots (P<0.05). Compared with the treatment of only waterlogging stress but no adding nitrogen, the chlorophyll contents in leaves, the activities of SOD, POD and CAT in leaves and roots, as well as the yield significantly increased from 13.28% to 26.98%(P<0.05), the MDA contents in leaves and roots significantly decreased 20.24% to 23.67% under the treatment with waterlogging lasted 6 days and applying N 60 kg/hm2 in both pot and field experiments (P<0.05), other indexes already restored to the level of the treatment of no waterlogging stress and adding nitrogen (CK) except the POD activities; The chlorophyll contents in leaves, the activities of SOD, POD and CAT in leaves and roots, as well as the yield significantly increased (P<0.05), the MDA contents in leaves and roots significantly decreased under the treatment with waterlogging lasted 9 days and applying N90 kg/hm2 in both pot and field experiments (P <0.05), but all the indexes could not restore to the level of CK. In the main planting region of winter rape, adding 60 kg/hm2 after 6 days waterlogging stress or 90 kg/hm2 nitrogen after 9 days waterlogging stress can restore and promote the plant growth and reduce the yield loss.