Abstract: The effects of different concentration of nitrogen treatments on the biomass, nitrogen and phosphorus partition in roots, stems and leaves of one-year-old Larix olgensis seedlings were studied by a sand culture experiment in greenhouse. The results suggested that N supply could significantly increase the seedling biomass. The biomass of roots, stems and leaves were the highest when 8 mmol/L nitrogen was applied in July, August and September. The biomass of leaves decreased gradually, while that of roots increased from July to September. The N concentrations increased significantly along with the N supply levels increasing. The mean N concentrations in roots, stems and leaves in the latter growth stage were 1.46, 1.48 and 1.17 times respectively more than that in the initial stage. The P concentrations fluctuated with the N levels change. The N stocks of whole plant increased markedly as the growth of plant, and it was 2.86 times more in September than in July. The N allocation also varied in leaf, stem, and root. The proportion of N allocation in leaf was the highest in July(60% in average). The proportion of N allocation in root increased with plant growth, which was the highest in September(41% in average). There was no obvious difference in N stocks among different N levels. The P stocks of the roots, stems and leaves were basically consistent with the N, but the variation scope was smaller than that of N.