The artificial pure Chinese fir plantation is designated as the ecological public welfare forest. In order to improve the diversity of tree species, replanting broad-leaved trees in pure Chinese fir plantation is an effective means of multi-function management. In order to optimize the spatial structure of forest stand, this paper proposed a method of spatial location and allocation when replanting based on Voronoi graph and Delaunay triangulation. The Voronoi graph and Delaunay triangulation are constructed by the spatial position of forest individual tree as the planar dissimilarity point. K-order adjacent relationship between trees can be quantized by Voronoi graph, Delaunay triangulation include distance and the angle informations between adjacent trees, and the gap between trees. This paper only considers the horizontal spatial structure of forest stand, the variation coefficient based on the Voronoi graph, the mingling and the competition index were chosen to describe respectively the distribution pattern, the mixed degree and the competition relationship, and the homogeneity target of spatial structure adjustment is established. Two plant initiation trees and dead trees were cut down before replanting. Two replanting tree species are respectively Koelreuteria paniculata, Liriodendronchinensis (Hemsl.) Sarg and Michelia odora (Chun) Noot. et B. L. Chen. The tree patch position was determined by the area size of Delaunay triangle. The spatial distribution of the trees was determined based on the K-order Adjacent, which achieved the optimization of forest stand spatial structure. The research object is the pure Chinese fir plantation, the tree species mingling of the stand before planting is very low, and it is between 0.011 and 0.063, its competition coefficient is between 0.699 and 0.833, competitive intensity is relatively small because of the young Chinese fir and no canopy, the variation coefficient based on Voronoi graph is between 1.662 and 2.354;The tree species mingling after replanting was improved, The mingling of the second time after replanting was greater than the first time, which was higher than before replanting. The species diversity, the mingling of tree species and the competition index were increased after replanting. The competition index of the second time after replanting is bigger than the first time, which is bigger than before replanting, which indicates that the competition strength is enhanced after replanting. The variation coefficient based on Voronoi graph is obviously decreased. The variation coefficient of the second time after replanting is less than the first time, which is less than before replanting. It is showed that the spatial distribution is more uniform after planting. The spatial distribution of stand can be adjusted by tree replanting based on Delaunay triangulation. The mingling of stand can be improved by tree replanting based on the K-order Adjacent, the more tree species, the more mixed degree. The tree replanting method can realize to improve the spatial structure of forest stand while optimizing the forest structure. This study can provide theoretical basis for adjustment and optimization of stand spatial structure while tree replanting, and can guide the artificial pure Chinese fir forest to the near natural forest, and achieve multi-function forest management.%杉木人工纯林被划归为生态公益林，为了提高物种多样性，在杉木纯林内补植阔叶树种是多功能经营的一种有效手段。为了在杉木人工纯林林木补植时尽可能优化林分空间结构，本文提出基于Voronoi图与Delaunay三角网的补植位置与空间配置方法。以林木个体所在空间位置为平面相异点构建Voronoi图和Delaunay三角网， Voronoi图量化对象木的K-阶邻近关系，Delaunay三角网确定相邻木间的距离、角度和林木间的林隙。考虑林分的水平空间结构，选取基于Voronoi图的变异系数、混交度和竞争指数分别描述林木的分布格局、混交程度和竞争关系，建立林木和林分空间结构调控的均质性目标。林木补植前进行两株萌生木与枯死木的抚育间伐，补植分两次进行，第一次补植栾树，马褂木，第二次补植观光木，依据林木间Delaunay三角形面积大小确定林木补植位置，依据K阶邻近林木关系进行补植林木的空间配置,以达到林分空间结构优化的目的。因为研究对象为杉木人工纯林，补植前林分的树种混交度很低，介于0.011～0.063，由于属于杉木幼龄，还没有郁闭，竞争指数介于0.699～0.833，竞争强度较小，基于V图的林木分布变异系数介于1.662～2.354；林木补植后林分树种混交度得到提高，第二次补植后树种混交度（0.191±0.007）比第一次补植后的树种混交度（0.186±0.005）有所提高，均明显大于补植前树种混交度（0.042±0.020），补植后不仅物种多样性增强，树种混交程度增强；补植后竞争指数增大，第二次补植后林分竞争指数（4.67±0.32）比第一次补植后林分的竞争指数（4.41±0.24）有提高，均大于补植前林分的竞争指数（3.92±0.20），表明补植后竞争强度增强；第二次补植后基于Voronoi图的变异系数（0.48±0.07）比第一次补植后基于Voronoi图的变异系数（0.55±0.10）降低，均小于补植前基于Voronoi图的变异系数（2.04±0.31），表明补植后空间分布更均匀。基于Delaunay三角网进行林木补植能够调整林木的空间分布，基于K阶邻近的林木补植空间配置能够尽可能提高补植林木混交度与林分混交度，且补植树种越多，混交度越大，本文提出的林木补植方法可以实现林木补植在提高生物多样性同时优化林分空间结构。本研究为林分空间结构调整与优化林木补植提供理论依据，促使杉木人工纯林导向近自然林，实现多功能的森林经营。
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