Abstract: Through a study of small earthquake activities in various areas in Shandong Province, it is found that the small earthquake activity frequence in Boshan area in central Shandong Province has a relatively good corresponding relation with M4-5 moderately strong earthquakes occurred in recent several years in Shand0ng region. Before a moderately strong earthquake, the small earthquake activity in this area will undergo a "concentrated-quiet-earthquake occurrence" process, so it is considered as a "seismic situation window" for monitoring the moderately strong earthquake activity in Shandong region. Since it was formally used, before the Southern Yellow Sea and Cangshan M5 earthquakes, this window showed notable anomalies conforming to prediction index and played an important role in prediction.