The dextral compressive tectonic zones of N10°-30°W in Northeast Qinghai-Xizang Plateau is generally known as Hexi System. The system consists of three upwarped districts, four depressions and some fault zones located between the both of them. Its activity influences to the midlower crust, even to the bottom of lithosphere in eastern border. The Hexi System evidently control seismicity. Moderate earthquakes or greater ones mainly occurred in some parts where the edges of the first-class upwarped districts and the NWW fault intersect.