The spatial pattern of forests depends on their internal characteristics, interspecific relationships, external environmental characteristics, and interactions with different individuals of the same species plant. At the same time, it also determines the spatial situation of growth competition among trees and provides habitats of animals, plants, and microorganisms and it is one of the important research contents of forest ecology. We used the survey data of 10.4 hm² plots in the Xiaoxing'an Mountains Liangshui Nature Reserve to analyze the composition and distribution of arbor species in the plots. We used the calculation method of mixed degree to explore the distribution of same species adjacent trees around large-diameter individuals, and analyzed the causes and the role of large-diameter individuals. Research indicates:(1) Large diameter individuals (DBH is greater than 50.0 cm) have the lowest degree of mixing with neighboring trees in the range of 5-6 m around it, and it is easy to form the same species adjacent trees circular structure surrounding large diameter individuals (hereinafter referred to as the central tree), which promotes the future forest succession and renewal to a certain extent; (2) The middle and small level individuals within the range of 15 m from the central trees (diameter class 1 of adjacent trees (1.0 cm < DBH < 5.0 cm), diameter class 2 of adjacent trees (5.0 cm < DBH < 10.0 cm), and diameter class 3 of adjacent trees (10.0 cm < DBH < 30.0 cm)) maintain a high degree of mixing with the central trees. However, the degree of mixing of diameter class 4 of adjacent trees (30.0 cm < DBH < 50.0 cm) and diameter class 5 of adjacent trees (DBH ≥ 50.0 cm) with the central trees were significantly decreased, and diameter class 5 of adjacent trees was the lowest. This phenomenon is closely related to conspecific negative density dependence (CNDD) and species coexistence mechanism. In this paper, by studying the distribution of trees in different species and different growth stages (different diameter classes), we revealed the forest spatial pattern characteristics and the cause of formation of the trees around the large diameter individuals in broad-leaved Korean pine forests in Liangshui, and demonstrated the important role of large diameter individuals in controlling the structure of surrounding forests, maintaining species diversity and promoting forest succession, which provides data support for the sustainable management of broadleaved Korean pine forest. In addition, this study adopted single-time forest data. Whether the influence of large diameter individuals on the surrounding forest structure and species diversity will change with time remains to be further studies. Therefore, long-term dynamic observation study of forest community is urgently needed.