Abstract: An investigation was made into several landslide cases in recent years to summarize common characteristics of the landslides composed of saturated loose granular materials. These landslides typically exhibited complete collapse accompanied by unique phenomena such as abrupt failure, static liquefaction, and high-speed and long-runout motion. Their failure mechanism was extremely similar to the diffuse failure as discovered in the field of soil mechanics, and hence can be viewed as a new type of landslide failure mode. In addition, the primary failure mechanism of the diffuse landslide was discussed through physical simulation experiment. The results indicate that diffuse landslides generally occur to saturated loose granular materials with evident strain-softening characteristics, such as silt, sand, and gravel soil. As the stress in the soil reaches the critical state, any external micro-disturbance may trigger an abrupt failure of the slope. The abrupt failure is typically accompanied by an excess pore water pressure and a phenomenon of static liquefaction. After loss of stability, the soil generally undergoes a rapid flow-like mass movement, which may result in catastrophic geological disasters and should be highly valued.