Abstract:Taking two typical widely distributed natural evergreen broad-leaved forest-Polyspora speciosa forest and Castanopsis fargesii forest in southwest subtropical as object,we analyzed their spatial structure characteristics with three space structure parameters including mixed degrees,the number and angular size scale according to species composition.Results indicated that:there were 8 and 9 kinds of species in the arbor layer of the P.speciosa forest and C.fargesii forest.The two stands had the advantages in dominant species density and basal area per hectare.The average mingling degree of the two forests were above the middle mingling degree,0.61 and 0.73,respectively.The species segregation of C.fargesii forest communities was better than that of P.speciosa forest.The average neighborhood comparison values of the two stands were 0.47 and 0.45,respectively,which indicated that the majority of trees were in a moderate state.Trees in different diameter classes were distributed uniformly in the spatial structure of the constituent unit.The average uniform angle index was 0.523 in the P.speciosa forest,being aggregated distribution,while 0.517 in the other stand,being randomly distribution with slightly aggregated distribution.The mingling degree of two kinds of forests had significant differences,while the differences between the neighborhood comparison and uniform angle index were not significant.It can be concluded that C.fargesii forest has more stable community structure than P.speciosa forest.