Abstract: The NH4+-N/NO3--N ratio of nutrient solutions was shifted to study the effects of nitrogen forms on enzymes related to nitrogen metabolism of corktree seedlings (Phellodendron amurense). Nutrient solutions with a higher NO3--N than NH4+-N content were beneficial for growth, and the content of chlorophyll and soluble protein in leaves with this treatment was also high. The highest biomass occurred when the NH4+-N/NO3--N ratio reached 25/75. Glutamine synthetase (GS) activity in corktree seedlings increased with NH4 +-N ratio, whereas nitrate reductase (NR) activity increased with increasing NO3--N ratio. The nitrogen form and ratio in nutrition solution could control nitrogen metabolism by affecting GS and NR activities.