Abstract: The liquefaction mechanism to cause rapid and long runout landslides is discussed in this paper. Through ring shear tests under the drained condition and undrained conditions, combined with field investigation on different types of rapid and long runout landslides, it is concluded that spontaneous liquefaction can be triggered due to collapse of loose structure in sandy soil, while grain crushing liquefaction can be caused during the sliding process when the saturated soil in sliding zone is crushable. Based on the results, a model describing sliding zone extension to the sliding mass is proposed, and the difference in the sliding mass deposit caused by the two different liquefaction mechanisms is analyzed. The importance of grain crushing is emphasized in this paper. For landslide disaster prevention, it is important to investigate the susceptibility of grain crushing, as well as the soil structure.