Abstract: With the eco-function areas of the Hulun Buir grassland as the case study areas, the vegetation cover, topographic factor, soil erodibility, strong wind hours and wetness index were selected as the indicators to assess the importance of wind-prevention and sand-fixing function, and the assessment indicator system constructed using a combination Delphi Method and Analytic Hierarchy Process Method. The function importance of wind break and sand-fixing was evaluated for the eco-function areas in three periods (2000-2003, 2004-2007, 2008-2011) by ETM image data and GIS, and the dynamic change and spatial distribution pattern of single factor importance and comprehensive importance were analyzed. The result indicated that the vegetation coverage played the most prominent role in the wind break and sand-fixing function. From 2000 to 2011, the function importance increased first and then reduced, with the increase trend from east to west. The sand belt area was with highest importance while the temperate meadow steppe area and temperate steppe area were with light importance.