Abstract: With a background of global climate warming, the effects of permafrost changes on aboveground vegetation have attracted much attention. The effects of permafrost changes on distribution patterns of plant species diversities and biomass in the Dongkemadi River Basin (head water of Yangtze River) were investigated. 1) Species diversity indexes non-monotonically decreased as the depth of the permafrost active layer increased, and the maximal values of species diversity indexes occurred at about 2 m depth of the permafrost active layer (the Partrick index, Shannon-Wiener index and Simpson index are respectively 26.43±3.31, 2.06±0.38 and 0.83±0.08). 2) In terms of the vertical distribution of biomass, underground biomass was considerably larger than aboveground biomass, underground biomass occupied 63%-96% of the total biomass. 3) There was a significant correlation between biomass and depth of the permafrost active layer (R²=0.65, P<0.01 for aboveground biomass and R²=0.79, P<0.01 for underground biomass), and both aboveground and underground biomasses decreased as the depth of the permafrost active layer increased. 4) The depth of the permafrost active layer had a considerable influence on the vertical distribution of underground biomass at soil depths of 0-40 cm: when the depth of the permafrost active layer was about 1 m, there was little vertical variation of underground biomass; but there was an obpyramidal pattern when the depth of permafrost active layer was larger than 1.5 m. When the depth of this layer was larger than 3 m, the ratio of underground biomass with soil depths of 10-40 cm to total underground biomass increased as the depth of the permafrost active layer increased.