Abstract: In order to study the effect of different nitrogen form on the physiology of Jerusalem artichoke seedling under the salt stress, a sand cultural study was carried out under the nitrogen nutrition (NH₄⁺/NO₃^- as 4/1, 1/1 and 1/4) and salt stress. 1) The treatment of low concentration of salt stress had a little effect on the inhibition of plant growth, but high concentration of salt stress could remarkably inhibit Jerusalem artichoke growth. Under the same salt concentrations, the dry weights, relative moisture content, plant height and leaf area of Jerusalem artichoke increased with the proportions of NO₃^--N augment.2)With the increasing of salt concentration, PSⅡ system was significantly damaged, but the increasing of the proportions of NO₃^--N could reduce the damage degree of the PSⅡ system and improve ΦPSⅡ, Fv, Fv/Fm, Fv/Fo, Fm/Fo and q_P. Especially, nitrogen nutrition had the highest light use efficiency at the ratio of NH₄⁺/NO₃^- as 1/4. For example, under 100 mmol/L NaCl stress, compared with the treatment at the ratio of NH₄⁺/NO₃^- as 4/1, ΦPSⅡ, Fv, Fv/Fm, Fv/Fo, Fm/Fo and q_P of the treatment at the ratio of NH₄⁺/NO₃^- as 1/4 increased by 1.03, 1.15, 1.05, 1.26, 1.20 and 1.05 times, respectively.3)Too much salt supply could cause the imbalance of plant cell osmotic, however, under the same salt concentration, the increasing of the proportions of NO₃^--N could significantly promote soluble sugar and soluble protein production and the transfer to the roots, then maintained the balance cell osmotic effectively under salt stress.4)Under the salt stress, the membrane lipid peroxidation usually occurred in plants cells, but the proportions of NO₃^--N augment could promote the SOD, POD, CAT and APX activity which had a function of eliminating reactive oxygen species, then alleviated membrane damage which the excessive accumulation of reactive oxygen species caused in cell. For example, under 100 mmol/L NaCl stress, compared with the treatment at the ratio of NH₄⁺/NO₃^-as 4/1, SOD, POD, CAT and APX activities of the treatment with NH₄⁺/NO₃^- as 1/4 were improved by 1.19, 1.08, 1.18 and 1.11 times, respectively. So with respect to NH₄⁺-N, the increase of the proportions of NO₃^--N was more conducive to increase the accumulation of dry matter and water content, improve the activity of intracellular protection enzyme, maintain the stability of PSⅡ system and cell osmotic balance, then enhanced the resistance of Jerusalem artichoke to salt stress.