In the earthquake sequence of Wenxian Ms5. 0 event on Jun. 21,2006, in Gansu province, the aftershocks were rich, so the type of shock is mainshock-aftershock sequence. No moderate or strong earthquakes occurred in 100 years before the event, but ML ≥3.0 events had increased and occurred one after another with groups in one year before the mainshock. Until one month before, the seismic activity went quiet. No seismic gap and belt is formed.