S method, which superposes the change values of all survey points in same mobile geomagnetic survey line, can restrain the disturbance to single point and stick out the possible anomalous information of seismic geomagnetic field. In this paper the relationships between S anomaly and small seismic swarm, moderate-strong earthquakes in near region are researched, as well as the correlativity between the S anomaly in "seismic window" area and moderate-strong earthquakes in the connected region. At last the "Changes in same direction" phenomenon of δf values for all survey points in same survey line and in same time is discussed.