Abstract: Gully is the main region of soil erosion,in the meantime,it is also the main expression of loess landform evolution in the Loess Yuan Region.Taking Jiuxian Town as an example,this paper recovers the processes of gully development and soil erosion of the Loess Yuan Region in Luochuan County since Yuan Dynasty (A.D. 1267）.Both the on-the-spot investigation and the textual research method are applied.The paper calculates the gully development speed and the soil erosion intensity in different historic periods.The evolution processes of gully in the Loess Yuan Region are also analyzed.Since Yuan Dynasty,gully development speed and soil erosion intensity have the trend of aggravation.In the period when precipitation is comparatively rich,the gully development speed and soil erosion intensity are comparatively strong.It is the principal reason why natural erosion and man-made erosion lead to gully development and soil erosion violently since modern and contemporary age. Landform evolution process of gully is from the bystreet-shaped then to the V-shaped,finally to the U-shaped. The bystreet-shaped and V-shaped gullies are the key sections of soil erosion and water conservation in the Loess Yuan Region.

Key words: the Loess Yuan Region, gully development, soil erosion, Yuan Dynasty