With the methods of combining macroinvestigation with microexperimentation，and test analysis with site observation，land degradation caused by soil and water loss on slope fields is studied in hilly and gully areas of the loess plateau.The results show that soil and water loss on slope fields not only brings about surface runoff loss and topsoil fertility decline，but also causes the soil nutrient loss，soil physical property damage and weakened soil infiltration capacity.The direct result of soil degradation is the reduction of land productivity.The impacts of soil and water loss in different slope fields under different crops are productivity losses of between 21.9%and 80.0%.