Abstract: An investigation on the community structure and biomass dynamics of the Kobresia pygmea community was carried our mainly in a plot of 30m×30m, at the Haibei Research Station of Alpine Meadow Ecosystem from May to September in 1989. 35 species belonging to 30 genera and 11 families were recorded. Besides the first dominant species Kobresia pygmaea, the dominant species also included Stipa aliana, Saussurea superba and Festuca rubra, etc.. The 65.7% of the species were hemicryptophytes, and the other 34.3% were geophytes. The vertical distribution of both above and below ground biomass of the community showed a pyramidic pattern. The 91.8% of the above ground biomass and 90.4% of the below ground biomass were respectively concentrated in the 0—10cm layers above and below the ground.The seasonal biomass dynamic (Wi) of the different plant groups could be described by Logistic equations: Wi=Ki/[1 +exp (Ai-Bi·t)]; where t referred to growing days since the 21st April, Ki referred to the maximum biomass, i referred to different plant groups, Ai and Bi were constants. While the seasonal changes of the litter biomass showed a V-curve, i.e. the litter biomass was the lowest in Summer.The growing rates of different plant groups were different, but average growing rate of the community biomass was 2.79g/m2·d-1 in the growing season, and the net production of the community was 368.4g/m2·d-1 corresponding to an assimilated solar energy of 6655.16kJ/m2· a-1 among which the sedges, grasses, forbs and litter occupied 35.19%,23.33%,34.15% and 7.42% respectively.