At 01:45 a.m. on Jan 08, 2022, an MS 6.9 earthquake occurred in Menyuan County, Haibei Tibetan Autonomous Prefecture, Qinghai Province. Its epicenter is located on the northern Qilian-Qaidam block. In order to constrain the seismogenic fault and characterize the coseismic surface ruptures of this earthquake, field investigations were conducted immediately after the earthquake, combined with analyses of the focal parameters, aftershock distribution, and InSAR inversion of this earthquake. The preliminary study finds that the seismogenic fault of the Menyuan MS 6.9 earthquake is the Lenglongling Fault of the middle segment of the Haiyuan Fault zone, which is an active NWW-striking and left-lateral strike-slip fault. The total length of the coseismic surface ruptures is approximately 22 km. It consists of two sub-ruptures: the northern splay, longer than 18 km, with the left-lateral offset of ~2.1-2.3 m and decreases towards both ends, is along the western segment of the Lenglongling Fault, which is the middle segment of the Haiyuan Fault zone. The southern splay, with ~5 km long and lateral offset ~1.0 m, is along the east segment of the Tuoleshan Fault, which is the middle-western segment of the Haiyuan fault zone. It is a sub-rupture caused by the end effect of the main rupture westward motion. Together with the western segment of the northern splay, they formed an obliquely left-stepping pattern. Multiple rupture patterns exist, including linear shear fractures, obliquely distributed tensional and tensional-shear fractures, and pressure ridges. The earthquake also induced many icicles (formed by water blasting) and landslides in valleys. The coseismic surface rupture zone can be subdivided into two segments, separated by obliquely distributed pull-apart step-over: the southern segment, named Daxigou, strikes nearly E-W. The northern segment, named Liuhuanggou, strikes mainly along the NWW direction.