Abstract: There are many ancient landslides in the loess area. The slip mass of ancient landslide is incompact and fissured, it's easy to slide under the slope toe excavation. The landslides triggered by slope toe excavation have caused a great quantity of economic losses and have posed an enormous threat on safety during construction; hence there are practical significances to study on its mechanism. Focusing on Wangyao Village landslide in Yan'an, the effect of confining pressure and moisture to loess is obtained by triaxial test, the stress and strength change on the most dangerous slip surface during excavation are studied and the deformation and fracture mechanism of the ancient landslide resurrection are revealed based on numerical analysis. The results show that excavating on the toe of slope changed the stress distribution and the shear stress in middle and lower part of slope, making the sliding resistance decreased and sliding force increased, in the end, the sliding force exceeds the sliding resistance and then the landslides occurred.