Abstract: There are lots of landslides triggered by deserted cave dwellings that threaten people's life and property safety in the loess area. With Sanmutai landslide in Yan'an as a study case, the authors detected the variation regularity of moisture content and strength of loess during the deserting of cave dwellings and the building of houses beside the cave dwellings through laboratory test. The stress and strength change on the most dangerous slip surface were studied and the mechanical mechanism of the development of deformation and the failure of loess landslide were revealed. The results show that the deserting of cave dwellings and the building of houses beside the cave dwellings would increase soil moisture content and reduce soil strength, making it nearly impossible for the stress distribution in the lower part of the slope to resist the shear stress and thus causing the collapse of cave dwelling and the occurrence of landslides.