Abstract: The sediment yields of Jinsha River basin has shown a significantly in-creased trend in recent years.This research focuses on the Yuanmou County which is a typical xerothermic valley of Jinsha River basin.The sediment yields variation in Long Chuan River（Xiaohuangguayuan）,a river passing through this region during the period of 1956—2000 were analyzed.The annual sediment yield of the Long Chuan River has an increase tendency since 1950s.particularly,in 1990s.The mean annual sediment yield increased from 400×10⁴t（1971—1980） to 750×10⁴t（1991—2000）.By analysing the impact factors on sediment yields based on statistic analysis methods,it is shown that regional climate change,especially the increase in the quantity and intensity of rainfall,is the main reason accelerating the surface erosion and increasing the sediment yields of the river.At the same time,due to the rapid increase in the amount of livestock,rapid population expansion,lagged production methods and influence of crop market price, the land cover and the structure of land use have obviously changed during the recent 50 years.The decrease of land covered area,the increase of slope farmland and the decline of the area of shrub and grass,which have high values in soil and water conservation but relative low values in economic profit per unit,have heavily aggravated soil erosion and increased river sediments which extremely undermined the fragile ecology of xerothermic valley in Yuanmou County.Furthermore,the intensive gully erosion is another important inducement of the increase of sediment yields in Longchuan River.