In the northern section of the North-South Seismic Belt since 1970 activity characteristics of earthquakes with M_L ≥ 3.0 before M ≥ 6.0 earthquakes are analyzed,and discussed the calm or enhanced characteristics of the phenomenon. On the basis of the main seismic source mechanism and the differences of regional activity,the calm phenomena of M ≥ 6.0 earthquakes are analyzed in depth. The results show that there is clam anomaly of seismic activity of earthquakes in the epicentral area before main shocks. The calm characteristics and time of each region are different. The duration of the calm of earthquakes with M_L ≥ 3.0 in the epicentral area before main earthquake was closely related to the activity level before the main earthquake.