The effects of water and nitrogen supply on physiological characteristics of broomcorn millet root at jointing stage was studied by pot experiments,the study used the interaction of 3 water and 3 nitrogen levels ,‘5283 huang’ and ‘Jinshu 5’ two varieties as test materials.The results showed that:（1）Root weight,total root length,total root surface area were increased with increasing nitrogen application at equivalent moisture,while root to shoot ratio decreased;under the same amount of fertilizer,with increasing water supply,root morphological index rised raised and shoot ratio showed the opposite trend.（2）To some extent,proline and soluble sugar contents of root were decreased with the amount of nitrogen fertilizer increased appropriately under water stress.SOD activity and POD activity were decreased,root membrane lipid peroxidation was reduced.But the decline of the indicators was significantly different due to different moisture and fertilizer conditions and different varieties.（3）Under the condition of severe drought and nitrogen stress,osmotic adjustment ability and antioxidant enzyme activity of ‘5283 huang’ root was higher than that of ‘Jinshu 5’.It can clearly be seen that appropriate water and nitrogen supply treatment can effectively induce osmotic adjustment ability and antioxidant enzyme activities of millet roots increased,reduce injuries in adversity stress and increase the ability to drought resistance and nutrient stress.