Understanding endangering mechanisms of Paeonia decomposita, endmic to China, is very crucial to protect and utilize this valuable germplasm. However, little was known on the niche characteristics and relationships of Paeonia decomposita and associated shrubs species in dry valleys of Dadu River. We investigated niche breadths, niche overlaps and spatial associations of P. decomposita and associated shrub species in dry valley of Dadu River, south-wetern China.The standard niche breadth of P. decomposita, Berberis julianae, Zanthoxylum simullans, Quercus baronii, Cotoneaster diwaricatus, Rosa app., Berberis wilsonae, Cotoneaster horizontalis, Bauhinia faberi var. Microphylla was 0.745, 0.979,0.950,0.748,0.947,0.924,0.792,0.863,0.610,respectively. Niche overlapping values of P. decomposita and the dominate species B. julianae, Z. simullans ,C. diwaricatus, Rosa app. were over 0.50, which were higher than those between P. decomposita and the other species. Combined with the analysis of spatial associations of P. decomposita and associated shrub species in dry valley of Dadu River, it was concluded that P. decomposita had weak ability to utilize resources because of its small niche breadth, and was in a disadvantaged position within species competition, which significantly contributed to understanding of endangereing mechanism P decomposita.