Abstract: On May 28th, 2012, an M_S4.8 earthquake occurred on Tangshan fault zone, its main rupture surface is strike-slip type and consistent with the fault zone.The earthquake sequence is mainshock-aftershock type.Just two months before the earthquake, an earthquake belt made up of small earthquakes of M_L≥1.0 formed from Tianjin Hangu to Beijing Pinggu, which may be seen as an seismic-window to Tangshan old seismic region and has certain guiding significance to estimating the epicenter of moderate-strong earthquake in the future.