Forest spatial structure has always been an important topic of ecology research. This research has a key significance on the management and maintenance of forests. However, the research has yet not attained robust knowledge on these processes. Moreover, there is a lack of reliable supporting data, and research on changes in forest spatial patterns is not sufficient. Large trees in forest stands affect spatial pattern directly; large trees cause large gaps when they fall or become dead standing trees, thus resulting in changes in spatial patterns. In this study, we used 10.4 hm² of forest sample data at Liangshui Nature Reserve in the Lesser Khingan Mountains (Northeast China). We obtained location coordinates, DBH of each individual tree in the sample, and analyzed the forest spatial patterns to elucidate the distribution among individuals within the forest stand. We statistically analyzed the composition of tree species and explored the effect of large trees on the spatial distribution of adjacent trees. The results showed that a total of 24 tree species in 18 genera and 11 families were recorded among the 7412 individuals. Additionally, a circular structure of small trees surrounded a large tree, and the circular structure changed with the diameter of the small trees. The diameter class 2 of adjacent trees (5.0 ≤ DBH < 10.0 cm) form circular structures in the radius of 3-7 m from large diameter individuals and diameter class 3 of adjacent trees (10.0 cm ≤ DBH < 30.0 cm) form circular structures in the radius of 3-6 m from large diameter class individuals. However, the circular structure was not found in diameter class 1 of adjacent trees (1.0 cm ≤ DBH < 5.0 cm) and diameter class 4 of adjacent trees (30.0 cm ≤ DBH < 50.0 cm). The formation of a circular structure was closely related to the competition among individuals in the forest, and there was an internal relationship between structure and dynamic theory. Structure is also a manifestation of dynamic change in forests, which will appear or disappear with forest growth. In addition, the change in large trees' diameter class affects the distribution of the circular structure. The larger the diameter of the large tree, the narrower the scope of gather, the more obvious the circular structure. This shows that the traditional explanations that the degree of aggregation of adjacent trees decreases near large trees, and the larger the diameter of larger trees, the lower the degree of aggregation, are not always correct. However, this study used single-time data, further studies are required to determine changes in circular structures over time.