<p>Loess, which is sensitive to water, is particularly susceptible to catastrophic failure during water infiltration. Loess geohazards typically exhibit flow-slide characteristics, resulting in sudden failure and long run-out distances. To study the mechanisms of the strength degradation of loess during initiation and movement under the influence of water, stress-controlled and velocity-controlled ring shear tests were conducted under varying normal stresses by ICL-2 high-speed ring shear apparatus. The results revealed the following: (1) saturated loess consistently exhibits strain softening characteristics under shear stress, and the pore water pressure increases with increasing shear displacement, resulting in a pore water pressure ratio of approximately 0.6, indicating significant strain softening behaviour. (2) The pore water pressure can increase to 90% of the total stress, reducing the effective stress by more than 95%, leading to liquefaction at the sliding surface as the shear displacement increases. The high pore water pressure and reduced shear strength resulting from shear liquefaction promote the high fluidity of loess landslides. (3) As the shear rate increases, the residual strength and friction coefficient of saturated loess gradually decrease, indicating that the mobility characteristics are associated with the effect of the negative rate following saturated loess landslides. Additionally, the brittleness index increases with increasing shear rate. (4) The mechanism of the negative shear rate effect of water migration in the shear zone is revealed. An increase in the shear rate leads to greater particle crushing, causing water and fine particles to migrate, which leads to weakening by friction and a reduction in shear strength.</p>