Abstract: Response characteristics of cucumber seedlings to nitrogen (N) application rates and forms were determined for optimizing fertilization during seedling nursery period, ammonium nitrate phosphorus fertilizer as tested material (NO_3--N:NH₄ -N 0.9:1.0), the influence of different application rates of N on growth and nutrients uptake of cucumber seedlings were studied under providing NO_3--N and NH₄ -N simultaneously condition in this experiment. The results indicated that nitrogen application could significantly increase leaf area, plant height of seedlings but no statistical differences were found within the four N applied treatments (50~200 mg N/plant), compare with no N applied treatment (control). There were no significant difference between all N treatments in shoot dry matter accumulation and stem diameter of cucumber seedlings. N utilization inhibited root growth, with the decrease of root length, root surface area and root dry matter accumulation (especially at the rate of 100 mg N/plant), and root length decreased markedly with 0.5~1.3 mm and 1.8~2.6 mm root diameters. Significant effects were found in concentrations and contents of N, phosphorus (P) and potassium (K) of shoot, but no significant effects in P, K concentrations and N, P, K contents of root with different N application rate. Shoot and root growth status were taken into consideration, N application rates at 50 mg and 150 mg per plant could produce stronger seedlings.