Utilizing the data observed at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL), characteristics of land surface radiation and energy budget over the Loess Plateau of central Gansu in summer are analyzed in this paper. By studying the impacts of different weather conditions on micrometeorological characteristics, the asymmetric structure of diurnal variation of surface albedo appears in the morning of sunny days with larger albedo values. The surface energy budget on a sunny day has a larger amount of imbalance, compared with that on a cloudy day. Besides ,the shower on an obscure day can also lead to large energy imbalance. The unclosure of energy balance obtained by using OLS(Ordinary Least Squares) linear regression method is 19.6%.In the semi-arid area，the clouds and the precipitation cause about 25％ disturbances to each component of energy balance. Weakening impact of clouds and precipitation on surface energy budget is apparent and much stronger than Dunhuang Gobi. Furthermore, it shows that the mean climatic characteristics in summer relatively close to those of cloudy days with more clouds(5≤Mean total cloud amount <8). Moreover, the maximum daily average Bowen ratio in July reaches 4.1 and the monthly mean value is 1.95. The Bowen ratio in Yuzhong is much smaller than that in Dunhuang Gobi, which indicates the semiarid area is more humid than the extreme arid area.