Abstract: Damaosi is one of original karst tiankengs with underground virgin forest in Yunnan Pro-vince. The spatial point pattern analysis and the woody individual spatial structure parameters, including the uniform angle index, mingling degree and storey index, were used to estimate spatial pattern of the tiankeng’s underground forest community. We also analyzed the intraspecific spatial distribution characteristics and interspecific spatial association on the basis of the individual relative position information of plant community. The results showed that the spatial distribution of plant community in Damaosi tiankeng was random. Plant species in the forest were moderately mixed. The vertical stratification of this forest was relatively simple, with stable structure and mature development characteristics of climax forest community. The populations in this community were mainly clustered in spatial distribution, negatively correlated between species and stronger negative correlation on the same vertical level. The larger the difference in the vertical level, the smaller the space competition was. The negative correlation in space became weaker with the increases of spatial scale. Tiankeng ecosystem was one type of precious natural habitats and plant refuges with high ecological stability. The stable structure of tiankeng plant community had important implications for the ecological resto-ration in karst areas.