Nitrogen (N) and phosphorus (P) were important limiting elements for plant growth and development in the nature. N, P and their relationship were essential contents in stoichiometry. Different plant organs had different demands for N and P, therefore the allocation and trade-off of N and P played an important role in the growth and development of plants. In order to explore the N and P stoichiometric characteristics and allocation patterns of shrub organs in different successional stages of the mixed broadleaved-Korean pine (Pinus koraiensis) forest, and to understand the nutrient limiting factors and allocation strategies, the dominant shrub species in four successional stages (secondary birch forest, mixed broad-leaved forest, mixed broadleaved-conifer forest and the mixed broadleaved-Korean pine forest) were selected in Liangshui National Nature Reserve, Heilongjiang. In this study, to research the N and P stoichiometric characteristics and allometric relationship, leaves, twigs, stems and roots of shrubs were collected to analyzed. The results showed that the contents of N and P in different organs were significantly different. In addition, the contents of N and P in leaves were the highest, while those in stems were the lowest among all shrub organs. The N:P ratio of leaves was the highest (7.59), and that of roots was the lowest (5.47). N:P ratio in leaves, stems and roots were significantly different, but N:P ratios in stems, roots and twigs were not significantly different. The effects on N and P stoichiometry of the same organ in different successional stages of the mixed broadleaved-Korean pine forest were different. Specifically, the N content in leaves had a significant difference, though the difference in other organs was not significant. There was no significant difference in P content of shrub organs among the four successional stages. In fact, all of N:P ratios were less than 14, which showed that N was always a limiting factor for shrub growth in different successional stages of the mixed broadleaved-Korean pine forest. However, P had no limiting effect on the growth of shrubs. Our research revealed that the allometric relationship of N and P generally existed in shrub organs in different successional stages, presenting a significantly positive correlation. In general, there was no significant difference among the allometric slopes of shrub organs in the mixed broadleaved-Korean pine forest, indicating that the shrub adopted a conservative allocation strategy to adapt to the environment change and satisfy the needs of its own growth and development.