In order to find the reactivation mechanism of high-speed long-distance loess landslide in Jingyang southern highland of Shaanxi, the undisturbed loess and paleosoil samples were collected from sliding zones of large loess landslides, and the remolded soils were prepared from part undisturbed soils; repeated shear tests under different volumetric moisture contents were designed, and the relationships between indexes of residual shear strength and volumetric moisture content, and cosmic content were discussed. The results showed that the shear stress-displacement curves of undisturbed soil and remolded soil were both hardening type; the difference of residual shear strengths between undisturbed soil and remolded soil was significant under different vertical pressures.