Abstract: Abstract: Our study focused on different shape ratio of Nitrogen with the same quantity influenced the cucumber seedlings growth and influenced the key nitrogen metabolism enzyme: nitrate reductase (NR), glutamine synthetase (GS). Results showed, compared to single ammonium nitrogen (NH4+-N) supply, single nitrate nitrogen (NO3--N) supply is better for cucumber seedlings growth. When NO3--N: NH4+-N ratio at 75:25, the length of axial root, total surface area of root, total volume of root, height of strain, stem thickness, dry weight of earth proportion was the highest. NR activity was increased along with NO3--N increasing. When NH4+-N supply was less than NO3--N, GS activity was increased along with NO3--N increasing. When NH4+-N supply was equal to NO3--N, GS activity arrived peak. When NH4+-N supply was more than NO3--N, GS activity descent. In conclusion, NO3--N: NH4+-N ratio at 75:25 was the best proportion for cucumber seedlings growth.