General situations of 21 wells for observing dynamic of underground water and oil are introduced.The observation well net had adjusted in 1998,some wells are stopped observation and some wells are newly built,for strengthening seismologic surveillance of the Bohai sea and its surrounding area.The new principles selecting wells and the condition of observation well net adjusted are introduced.A preliminary analysis on reflecting earthquake ability of the net is made.It is considered the reflecting earthquake ability of the net is stronger.The oil output of some wells suddenly rises before earthquakes which occur in process of oil output change from high value to low value or after the oil output returned to normal.