With the data of Kobresia pygmaea growth period, plant height and yield during 1994 to 2004 from Qumalai county in the Yangtze river headwater region,we investigated the relationships between climate change and K.pygmaea phenology and biomass.The results indicated that:(1)The greenup stage and florescence of K.pygmaea appeared a shape of w in general.Under the background of regional climate warming,the growth season prolonged by advanced greenup and delayed florescence and wilting.(2)Biomass of K.pygmaea changed apparently during the past 10 years.The highest biomass of K.pygmaea in each month appeared in 1999,the lowest was in 1994.(3)The phenophase of K.pygmaea showed a significantly positive correlation (P<0.001) with monthly temperature in its growing season and a weak correlation with monthly precipitation (P>0.05).Average monthly temperatures appeared to be a prerequisite in germinating and growing of local herbs,especially from June-August.(4)Fresh-and dry-weight of K.pygmaea in growing season from June to August were positively associated with monthly average temperature,while fresh weight only had positive correlation with monthly precipitation.In summary,temperature has greater influence on vegetation biomass than that of precipitation in QinghaiTibet Plateau.