Abstract: According to the data measured in the network in the south of Chi Feng, the co-rresponding relation between the activities of small shocks in the region and Tang Shan earthquake or its strong aftershocks has been discussed, and "the window effect" of small shock activities can be stressed in this paper.The author explores the inter-nal relation between the small shock activities and the geological structures, and tries to give some clue to monitor strong earthquakes in the Beijing-Tianjin-Tangshan region.