Abstract: The Bayan Har Group consists of flysch deposits. The probability cumulative grain-size curves reveal that: there appear few turbidite-type curves represented completely by the suspension population and the curves are composed principally of the traction and suspension populations. Debris flows are the dominant genetic type of sandstone of the Bayan Har Group. Granulometric parameters show that: the average grain size in the Bayan Har basin becomes coarser with time and the sorting becomes better. The features of probability cumulative grain-size curves in different stages of the tempestite sequence are related to the composition of modified sandstone bodies.