Field investigations allow to constrain the co-seismic surface rupture zone of ～400 km with a strike-slip up to 16.3 m associated with the 2001 Mw 7.8 Central Kunlun earthquake that occurred along the western segment of the Kunlun fault, northern Tibet. The co-seismic rupture structures are almost duplicated on the pre-existing fault traces of the Kunlun fault. The deformational characteristics of the co-seismic surface ruptures reveal that the earthquake had a nearly pure strike-slip mechanism. The geologic and topographic evidence clearly shows that spatial distributions of the co-seismic surface ruptures are restricted by the pre-existing geological structures of the Kunlun fault.