A cylindrical structure，which is named as the icicle cast structure，was developed in the Quaternary clastic rocks in Qigequan area in western Qaidam Basin. According to the shape texture of the cylindrical structure and its relationship with other rocks，and by correlation with the studies of the similar structures，it is concluded that the origin of the cylindrical structure is related with the ice penitent. This kind of cylindrical structure can be named as the icicle cast structure. The icicle cast is cylindrical in shape and with diameter of 10～14cm and a height of 5～30 cm. Some show internal lamination while others not. The lamination is 0～15cm thick and is composed of mediumcoarse grained sandstones or finegrained conglomerate，gravelly mediumcoarse grained sandstones，sandstones and calcareous mudstones. It is inferred that the icicle cast is formed due to the icicle in the front part of the glacier plunging into the soft sediments and then being filled by the sediments after melting.