Abstract: The geological tectonic structure of northeast margin of the Tibetan Plateau correlates with that of Qinling-Dabashan region.The out flow of material in Tibetan Plateau lithosphere and regional structures interaction is the major tectonic stress acting on plate of the south part of North China.Based on these understandings,the seismic activity in south part of north China before 4 large earthquakes (M≥8) occurred on northeast margin of the Tibetan Plateau is analyzed.Seismic activity abnormity close to large earthquake epicenters is not obvious,but seismic activity in south part of north china is distinct.The process of seismic activity abnormity in south part of north china is visibly correlative with the strong earthquake brewing and occurring in northeast part area of Tibetan Plateau edge,The seismic situation display in outside areas give us some new idea on estimation the strong earthquake situation in northeast part area of Tibetan Plateau edge.