The Altyn Tagh fault，a major strikeslip fault system in NW China，is consists of the main fault and the subsidiary faults with a distribution pattern corresponds to a simple shear model. Shibaocheng Basin is located in the south of the eastern section of Altyn Tagh fault，confined by Qilian Mountains，covered an area of approximately 3〖KG*3〗000 km2. The sedimentary characteristics，such as the Pliocene stratigraphic features，conglomerate gravel compositions and paleocurrent，has been studied. The southern fringe of the Shibaocheng Basin，located at south of Tudaban，is composed mainly by the conglomerate and pebbly sandstone，which limestone gravel components accounted for more than 80％. The eastern edge of Shibaocheng Basin，situated near Shibaocheng Town，is consist of sandstone and siltstone with some conglomerate，which gravel compositions mostly are granite，schist，gneiss and other metamorphic rocks. The sedimentary center of the basin is located in the vicinity of Shuangquanjingzi，close to the side of the Altyn Tagh fault. The paleocurrent direction of Pliocene formation was from SE to NW and NWN. The terrain of Shibaocheng Basin was gradual lowering from South East to North West during Pliocene. The source area of the western Shibaocheng Basin was the Daxue Mountains and some other mountain，which is located in the southern to the Shibaocheng Basin. The source area of the eastern Shibaocheng Basin was the uplift mountains near the Shibaocheng town. Shibaocheng Basin is a strikeslip branch basin formed by interaction of the Altyn main fault and its branch faults. The Basin began to extend in Pliocene and its extensional width is now about 30～40 km. The extending rate of the Shibaocheng Basin is about 066 cm/a. Based on the same rate，the displacement of the Altyn main fault is approximately estimated 218 km from Oligocene in SubeiShibaocheng segment.