Abstract: Some work about the measurements of the niche breadths and niche overlaps of the plant population of the barren hillsides was carried out in the arid valley of the upper reach of the Minjiang River.The results are as follows.(1)The Simpson index and the important values are more suitable for measuring the niche breadths and the Pianka niche overlap index and the summed dominance ratios are more suitable for measuring the niche overlaps.(2)The community is co -dominated by Selaginella pulvinata,Allium sikkimense,Carex lanceolat,Sedum multicaule and Capillipedium parviflorum.Their niche breadth values were 32.34,25.89,29.30,22.92 and 25.77.(3)Niche overlap exist in most species pairs of the plant community of the barren hillsides of arid valley in the upper reach of Minjiang River.But many values of the niche breadth are very small.It indicated lower niche differentiation without enough level of interspecific association such as competition,reciprocity etc.

Key words: niche, plant population, barren hillsides of arid valley, the upper reach of Minjiang River