The seedlings of Isatis indigotica in hydroponic cultivation,which seeds were planted in media,were treated by N deficiency and N recovery,and the growth and contents of nitrogen metabolites were analyzed to study the effect of N deficiency and N recovery on growth and nitrogen metabolism of I.indigotica seedlings,and so as to increase the yields,quality and nitrogen utilization.The results showed that:(1)The content of chlorophyll,nitrate,indirubin,glutamine synthetase (GS) activity were the largest,and plant height,main root diameter,fresh weight and dry weight of root,fresh weight and dry weight of leaf and root activity were minimal under the normal treatment.(2)N deficiency could increase main root diameter and dry weight of root,improve the root activity and the activity of nitrate reductase (NR),promote the accumulation of free amino acid in the leaves.Meanwhile,it reduced the GS activity,the contents of nitrate,soluble protein and indirubin in leaves and free amino acids in roots.There were almost no influences to the content of indigo in leaves under N deficiency.(3)N recovery enhanced the weight of plant height,root length,root fresh weight,leaf fresh weight,dry weight of leaves,improved its root activity and reduced the NR and GS activity.Compared with normal process,N recovery reduced the contents of nitrate nitrogen in leaves,improved the content of soluble protein,indigo in leaves and free amino acids in roots.There were little influences to the contents of free amino acids and indirubin in leaves.These results indicated that N recovery after N deficiency was beneficial to the leaf growth and the increasing of indigo of I.indigotica seedlings.