Abstract: Field survey shows that the macro-epicenter of October 6, 2008 Ms 6.6 Damxung earthquake is located at northern Yangyi graben in the north section of the Yadong-Gulu rift. The maximum intensity of the Damxung earthquake is Ⅸ degree and lies at Yangyi village (29°43.3′N；90°23.6′E). The main boundary normal fault of Yangyi graben is NNE-trending, dipping to east and located at west side of Yangyi basin. It is main seismogenic tectonics on the Damxung earthquake and controls the site of macro-epicenter, pattern of the iso-seismal contours, distribution of meizoseismal region and aftershocks. The field observation and focal mechanism solutions from HRV and NEIC indicate that the Damxung earthquake of October 6, 2008 occurred as a result of normal faulting along the western boundary fault of Yangyi graben. The normal faulting that caused the earthquake is a consequence of predominantly east-west oriented extensional deformation that is distributed in southern Tibet and ultimately arises from the convergence of the India plate northwards with respect to the Eurasia plate. Recently, the frequent strong earthquake activity occurred around Qinghai-Xizang plateau as a result of the regional stress field adjustment after the Ms8.0 Wenchuan earthquake.