A.D. 600 December 16, a strong earthquake occurred in an area including Tianshui, Gansu Province and Longxian, Shaanxi Province, which caused serious damage and social impact. For a long time, there were different understandings of its exact magnitude, epicenter and epicentral intensity, the seismogenic structure was also unclear. The Qin-Long area was a transitional zone between the southwestern margin of the Ordos block and the Qilian fault fold belt of northeastern Qinghai-Tibet block. It was significant to detailedly study A.D. 600 Qin-Long earthquake and discuss its seismogenic structure. The historical datum on A.D. 600 Qin-Long earthquake were collected and the previous works done by other scholars were also consulted. In Addition, A few of supporting information that was possibly related to this earthquake was discovered. Through studying the historical datum and analyzing the damages on this earthquake, the epicenter of A.D. 600 Qin-Long earthquake may located between Tianshui and Longxian, which is closer to the latter. Its epicentral intensity was inferred as IX and magnitude was about 6(3/4). The orientation of the long axis of the meizoseismal area was roughly consistent with Longxian-Baoji fault zone. By conducting the field investigation and comprehensively analyzing datum of this earthquake, the seismogenic structure of A.D. 600 Qin-Long earthquake may be concluded as Badu-Longwei segment of Guguan-Xiangong fault zone.