Abstract: The present study aims to reveal the implication effect of nitrogen on root growth and development of Picea abies, therefore to provide a basis for the regulation of root development with fertilizer. Three-year-old plantlets of Picea abies were employed and tested regarding their growth and development indexes of roots under different doses supply condition of nitrogen in pots. The obtained results indicated that all the tested doses of nitrogen, including N-6 (6 g urea containing 46% nitrogen for each plantlet), N-9 (9 g urea containing 46% nitrogen for each plantlet) and N-12 (12 g urea containing 46% nitrogen for each plantlet), consistently had a positive effect on roots in length, surface area, average diameter and volume, when compared to the control. The biomass and nitrogen content of roots and plantlets, the ratio of total root biomass of plants and the root-crown ratio in biomass also increased under the treatment of nitrogen. However, the regulated effect of nitrogen seemed to be different in dosage. The positive effect from N-9 appeared to be the most impressive (P<0.05) in that this dosage had a significant change of root morphology over 1.3 fold (1.38-1.89 fold) of the control, while the biomass of roots and plantlets, and the root-crown biomass ratio of plants were found to be also higher than that of the control at a significant level (P<0.05); moreover, the nitrogen content of roots and plantlets presented a 73.2% and 80.9% gains, respectively.