Abstract:A hydroponic culture experiment was conducted to study on the physiological characteristics and growth of Apium graveolens L.var.dulce DC.seedlings under the different NO3- concentration (0,1,5,10,15,50,100 and 150 mmol·L-1).The results showed that:(1)With NO3- concentration increased(1~50 mmol·L-1),the heights,biomass,shoot/root ratio and leaf area of the seedlings increased;the absorption of N,P,and K nutrients improved;the content of chlorophyll and the MDA increased;and the activities of POD and CAT increased.(2)When the NO3- concentration was equal to or higher than 100 mmol·L-1,the biomass and the content of chlorophyll decreased;the absorption of P,and K nutrients reduced;the MDA,soluble protein and sugar content,SOD activity appeared its highest peak;and the activities of POD and CAT decreased.We can concluded that the NO3- concentration of 15 mmol·L-1 favored the growth of celery;and the NO3- concentration of 100 mmol·L-1 caused the nitrate stress to the plant growth and resulted in injury to membrane lipid peroxidation,but the anti oxidation enzyme and osmatic adjustment substance could adjust themselves to avoid nitrate stress harms,which led to some tolerant ability of Apium graveolens L.var.dulce DC to nitrate stress condition.