To reveal the impact of landscape ecological risk (LER) of land use change and its spatiotemporal variation at the watershed scale, Bailongjiang watershed, a typical transitional ecotone between Loess Plateau and Tibetan Plateau, was chosen as the study area. Based on the data integration analysis platforms of GIS technology and Fragstats 3.3, the assessment method of land use LER was constructed with the incorporation of the environmental vulnerability degree and landscape ecological loss degree. Spatial distribution of landscape ecological risks of land use change in the study area was analyzed by means of spatial autocorrelation. The results showed that:the land use changed obviously from 1990 to 2010 in the watershed. The area of forest land and built-up land increased gradually while the cultivated land and grassland decreased. Unused land and water cover area were fluctuated during the research period. There was some obvious spatial difference of LER levels in the watershed. The LER level of the area in the northern and northwestern of Bailongjiang watershed was higher than that of the area located in the western, southern and eastern mountainous area of the watershed. Furthermore, the moderate LER area increased remarkably while the low-risk area and high-risk area both decreased. The agglomeration features of the LER were obvious and value of LER charactered as notable positive spatial correlation. The change of LER might be closely related with human activity, land use intensity and structure.