Basic conditions of Zhuanggu-25 well in Shengli oil field are introduced.Change characteristics of oil output before earthquakes and reflecting earthquake ability of the well are analysed.The results show that oil output of the well suddenly rose with gush sometimes before earthquakes.The larger the magnitude,the larger the anomalous amplitude and the longer the lasting time of the anomalies.Various degrees of anomalous changes of oil output of the well appear before most M_L ≥ 4 and M_L≥ 5 earthquakes in a range of 200 km and 500 km distant from the well respectively.Mechanism of reflecting earthquake of Zhuanggu-25 well is discussed in last.