Abstract: Evapotranspiration (ET) is an important component of hydrological cycle of terrestrial ecosystem. To study the seasonal and interannual ET variation patterns of typical ecosystems is essential to better understand the water cycle process and to provide reference for the rational utilization of water resources. By using eddy covariance method, this paper studied the seasonal and interannual variation characteristics of ET and water budget in an alpine shrub meadow ecosystem in Haibei of Qinghai from 2003 to 2011. There was an obvious seasonal variation of ET in the study area in 2003-2011, with the maximum (4.4-5.7 mm·d^-1) in the vigorous growth season (July-August) and the minimum (0.09±0.04 mm·d^-1) in January or December. The annual ET varied greatly among the nine consecutive years, being 451.3 mm in 2010 and 681.3 mm in 2007. More than 70% of the annual ET occurred in the growth season from May to September. The average ratio of annual ET to  annual precipitation was 1.06±0.17, indicating that the water budget of this ecosystem was nearly balanced at year scale, and almost all the precipitation was released into atmosphere by ET.