As the first metal mine where mining is conducted under the seafloor in China,Xinli gold Mine is located at the side of Bohai Bay in Shandong Province.In order to prevent the displacement or collapse of host rock affected by mining activity,avoid mine flooding accident of seawater bursting into mine excavations,seawater hydraulic filling with high concentration of total tailings was conducted to control deformation and displacement of host rock around a stope,avoid surface subsidence,increase ore recovery,and improve safe working condition.Preferentially,cut-and-fill stoping is performed.A series of lab testing results show that total tailings (or cemented total tailings) can be placed in the mined domain.In practice,dilute slurry from mill plant are pumped directly and continuously to tailing silos and densified by tailings settling down naturally.A combined compressed air-and-seawater slurrying technique in filling station is optimized to increase pulp concentration.Dewatering facilities in stope pick up dewatering speed and the inclined-face filling method is implemented to restrain slime conglomerating on the surface of filling body.As results,the utilization factor of total tailings is up to 90%during test of unclassified tailings filing or cemented filing,the concentration of filling slurry that is transported by gravity is 73%to 75%,and later work in stope can be done in 3 days after filling.