By dividing the semi-arid and arid regions into three parts: arid region in the northwest, Loess Plateau, and cold region in the northeast, the regional differences in the diurnal variation of land surface radiation and energy processes in the semi-arid and arid regions are investigated using the data measured during July and September, 2008, provided by the Experimental Co-observation and Integral Research in the Semi-arid and Arid Regions over northern China. The results show that pronounced regional differences in land surface radiation and energy processes are seen in distinct climatic zones and the differences are primarily attributed to the regional differences in available water either in land or in the atmosphere. Consequently, the studies of the regional differences in land surface processes to a large extent are the analyses on how the arid climate for different intensities affects the land surface processes. For radiation components, downward short-wave radiation decreases with the latitude increasing, and the upward short-wave radiation is largest in the arid region and smallest in the cold region. The downward long-wave radiation is strongest in the cold region and weakest in the Loess Plateau while the upward long-wave radiation is obvious in the arid region and weak in the cold region. For energy components, 70% of the land surface available energy is consumed by heating the atmosphere in the arid region, and the remaining 30% is used for evaporation and heating the soil. In the Loess Plateau, however, only 30% of energy goes to atmosphere heating and 50% is lost to evaporation. Roughly half the energy is lost to evaporation in the cold region, and most of the other half is used for heating atmosphere.