Abstract: We took the 25-year-old Cunninghamia lanceolata ecological forest in Fushoushan National Forest Park of Hunan Province as the research object. Analysis revealed that there was a negative correlation between competition index and the diameter at breast height (DBH). Based on this,it was confirmed that the weight of weighted Voronoi diagram was the reciprocal of DBH. Competition unit was determined by using weighted Voronoi diagram tool in Arcgis software, and the W_V_Hegyi competition index was proposed based on weighted Voronoi diagram. Finally, the comparative analysis among Hegyi, V_Hegyi and W_V_Hegyi competition indexes revealed that: 1) the correlation between competition index and DBH ranked from strong to weak as W_V_Hegyi V_Hegyi Hegyi; 2) the relationship between the three competition indexes and DBH followed the power function, and the order of curve fitting degree was in W_V_Hegyi V_Hegyi Hegyi; 3) the sorting of average competition index in sample plots was in V_Hegyi W_V_Hegyi Hegyi. The above comparative analysis proves that W_V_Hegyi competition index is more accurate than Hegyi and V_Hegyi in reflecting the competitive relationship among trees.