Abstract: By tectonic analysis of the images of small earthquake activity and focal mechanism data of earthquakes with magnitude of more than 4.0 (Ms), a distribution map of focal tectonics in North China has been obtained, which shows a conjugate shear tectonic framwork intersected by four NNE-NE and one NWW-NW seismotectonic zones.Each seismotectonic zone consists of a series of conjugate shear tectonics.From the conjugate fracture characteristics of four large earthquake sequences occurred in the zone, it can be found that the seismogenic and earthquake-controlling function of conjugate seismic tectonic is the mechanism of the formation of seismotectonic zones.