Abstract: 【Objective】Understanding the spatial structure of forests is important for developing sustainable forest management practices. The Pinus massoniana forest is an important protected forest type in the Three Gorges Reservoir area. This study was conducted to provide a theoretical basis for further analyzing forest succession trends and taking reasonable management measures for forest protection by analyzing the vertical structure characteristics of the P. massoniana forest.【Method】 Using the P. massoniana forest in Jiulingtou Forest Farm, Zigui County, Hubei Province as the research object, sample plots with sizes of 50 m × 60 m, 50 m × 60 m and 50 m × 50 m were investigated, and the principle of the canopy competition(in height)for light was examined to divide the vertical structure into an upper layer, middle layer and lower layer while considering the ecological characteristics of the canopy photosynthesis at different heights. The diameter at breast height(DBH)distribution, tree species composition, and spatial structural characteristics were analyzed. 【Result】 ①The average DBH increased with the vertical layer, and the average DBH values of the lower, middle to the upper forest layer were 7.34-8.95 cm, 14.42-18.15 and 24.48-26.06 cm, respectively. There was a significant difference in the volumes among the different layers. The upper layer showed the highest proportion of the total forest volume of 63.06%-76.78%, while the volume proportion of the lower layer only occupied 4.32%-7.10%. ②The diameter class increased as the vertical layer increased, while stand density decreased. The upper layers were mainly distributed in classes 22 and 30 cm, showing an irregular multi-peak curve. The middle layers were mainly distributed in classes 10, 18 and 22 cm, showing a mainly left-skewed peak. The lower layer showed a typical inverted “J” distribution, indicating that stand density decreased sharply with increasing diameter grades. ③ The main tree species in the lower layer were native hardwood species, and this layer represented the species composition of the whole stand. At higher forest layers, the number of tree species generally decreased. Although P. massoniana was the dominant tree species in the upper layer accounting for 69.72%-94.62% of species, its proportion decreased sharply as the vertical layer declined, demonstrating that the regeneration environment of P. massoniana forest benefitted the growth of native hardwood species. ④The change in the W(uniform angle index)value among the different layers showed no obvious regularity, with the stands generally presenting clustered or random distributions. The U(neighborhood comparison)value, M(mixing degree)value, and tree competition index increased as the forest layers declined, indicating that as the forest layer decreased, the degree of DBH differentiation became clearer, degree of tree species isolation was higher, and competition among individual trees was greater. ⑤The “W” distribution frequency of each layer generally showed a normal distribution. The proportion of trees showing a “W” value of 0.5 ranged from 46.03% to 63.33%, indicating that most trees were randomly distributed. However, trees in the lower layer were mainly clustered. In the upper layer, the proportion of superior trees was the largest, and the proportion of sub-dominant or dominant trees was larger than that of less inferior or inferior trees in the middle layer. In contrast, the proportion of inferior trees was the highest in the lower layer. The proportion of trees showing intensity mixing and extreme intensity mixing in the lower layer was much higher than that for zero degree and weak degree mixing; moreover, the tree competition index reached a maximum in the lower forest layer, indicating that the individual trees in the lower layer were subject to greater competition pressure from other tree species. As competitiveness of trees increased, the volume was reduced.【Conclusion】In the future, the P. massoniana secondary forest in this region may show succession to mixed forests with broad-leaved trees and coniferous trees in the same proportion, or become mixed forests with more broad-leaved trees and fewer coniferous trees. The main regulation layers of P. massoniana secondary forest in this area are the middle layer and lower layer. Based on easily obtained parameters, models that can accurately determine logging of trees should be built.