Abstract: Field experiments, including four levels of N application 0, 18, 24, 30 g N·m^-2, were carried out to clarify the effects of nitrogen fertilization on N accumulation and translocation in lea-ves as well as the seed quality of oil peony (Paeonia ostii ‘Fengdan Group’). The results showed that the nitrogen application significantly increased the height, canopy, flower diameter and flower dry mass. The heights under the treatments 24 and 30 g N·m^-2 increased by 14.7% and 15.2% compared with CK, respectively. Moreover, the nitrogen application improved seed yield. The highest seed yields were acquired under the treatments 24 and 30 g N·m^-2, which were 15.2% and 15.4% higher than that of CK, respectively. The N accumulation and translocation in leaves and the N accumulation in seeds all increased with the nitrogen application level. The greatest leaf contribution proportion was acquired under the treatment 24 g N·m^-2. The nitrogen application significantly increased the contents of protein N, total amino acid, and some saturated and unsaturated fatty acids in seeds. In this experiment, the N input of 24 g N·m^-2 was optimal to obtain the higher N translocation amount, N translocation efficiency and N contribution proportion from leaves to seeds, seed yield as well as the contents of protein N, amino acid and unsaturated fatty acids.