Abstract: Because of the excessive mining of confined water in a long period, the groundwater level in Daqing City has continuously declined to form the cone of depression. Based on the multi-year data of mining amount of groundwater resources and dynamic monitoring for groundwater, the formation and developing trend of the depression cone are analyzed. The result shows that the size of the depression cone is directly controlled by the mining amount of groundwater. The variation of water level is positively correlated to that of the mining amount.