Abstract：Aiming at the character of long-distance high-speed movement of Yigong landslide，and based on the advantage of large displacement shear test of ring shear apparatus，ring shear tests with different shear speeds and those under drained and undrained conditions are carried out to learn the mechanism of long-distance high-speed landslide. Results show that the pore water pressure cannot dissipate punctually，and the pore water migrates to the shear plane slowly during the experiment. Water content and fine particle content of the shear plane are higher than those of the original and other layers obviously，which leads to the liquefaction of shear plane in the consolidation shear test. Effective internal friction angle of the consolidation undraining shear test is greatly lower than the draining one；the higher the shear speed is，the lower the strength is. This can interpret the formation of Yigong long-distance high-speed landslide.
