The middle part of loess plateau is a typical agricultural area,and the most significant property of agriculture in this area is that the hilly and slop land are opened up to increase crop production.Therefore,soil and water loss is the major problem to limit the economic development in this area due to unreasonable social economic activities.The factors affecting soil erosion by human activities were evaluated through the combination of typical investigation and analysis.The results of the destroy of vegetation and underestimating soil and water conservation works in industrial development are the main factors affecting soil erosion by human activities.