The northeastern marginal area of the Qinghai-Tibetan plateau is one of the most tectonically and seismically active regions in China since Quaternary, especially late Pleistocene. It is also one of the regions which are of the highest great earthquake (Ms
≥ 7) frequency. A detailed research on the types of the seismic faults,their behaviours,distribu-tion,the features and the relations with the existed and their relation to the pre-existing faults in 19 large historical earthquakes and 10 fossil earthquakes was made in the region with a resulte of the division of 10 seismotectonic zones. This is expected to contribute to long term prediction research on large earthquakes (Ms
≥ 7)in the region and to the crustal stability study as well for damage reduction.