Objectives: Some avalanches or landslide—debris streams are of many characteristics, such as large volume, high speed, longdistance of movement, polymorphic existing, changes in direction, many motion stages, impact force and megadestroying energy. In fact, the high speed and longdistance of the movement occur primarily in the stage of debris streams after rock or soilmass broken up. Methods: The rapid and longdistance of the movement are related with the scale, component and structure of substance, difference of landform in elevation, valley features, induced factors and environmental condition which passed by avalanches or landslide. The deforming and breaking down types of rock or soilmass slopes are often being a chain of action process which includes creeping, fissuring, shearingoff, sliding, rushing out, breaking up and eventually to be debris stream. Mechanism of the avalanches or landslide can be explained through the existing theories such as residual strength of soil or rockmass, creep action principle and effective stress or porous water press effect. At present, mechanism of the debris stream is complex that it is interpreted through transformation of potential to kinetic energy, buoyant force of gaseous fluid and motion of pellet flow. The understanding from actual examples of avalanches or landslide—debris stream is, the above three recognitions are not independent each other, but different gradation from macroscopic view to microcosmic grain action and mutual complementary in different measurements. Results: Author suggests that the value of the speed of avalanches or landslide—debris stream vanguard is arriving 5m/s to be as lower limit of rapid movement based on the adult to flee for one’s life. The ratio of H/L is less than 0.4 can be as criterion of longdistance of avalanches or landslide—debris stream in which H is difference of landform in elevation and L is horizontal distance from beginning to end of the motion. Basic disaster models of the avalanches or landslide—debris stream include direct pushing down, breaking up destruction, colliding and pounding, air wave blowing, turbulent current and tornado, blocking dam to be lake and bursting floods, etc.