Field observations were carried out in grasslands in a semi-arid area in China in order to analyze the mechanism of desertification, and the micrometeorological characteristics were examined in relation to desertification. Additional measurements were carried out over a dune and a vegetated area for comparison. Albedo values over the grassland which changed with grass growth, were significantly different from those at the humid vegetation site. The values were higher when the amount of grass was small, and changed with the surface conditions of dry soil and vegetation. Wind profile over the grass showed a logarithmic curve during the measurement periods, while that over the dune in the daytime was similar to a turbulent mixing layer, which prevented plant growth. Evapotranspiration of the grassland ET was 2.8 mm/day in early August, while it was less than 1 mm/day in the dry season. The heat budget of the grassland undergoing desertification was close to that of the dune.