Abstract: In order to have a backill mining in Wangzhuang Mine, a backill material with high water swelling features was researched and developed.A study on th e goaf backfill system and technique was conducted.The backfill material had an good swelling, short setting time, high early strength, flow transportation and other feat ures.The material would be in liquid within two hours and have a good flowability and flow transportation.After the first two hours, the material would begin to consolidat e and swell and would actively connect with the goaf roof.After twelve hours, the uniaxial compression strength would be reached at 0.5 MPa and after 28 days, the uni axial compression strength would be reached at 2.2 MPa. The results showed that after the high water sweling material applied to the backfill mining, the pilot roof pres sure peak of the coal mining face would be highly reduced and the mine pressure behavior would not be obvious.The max convergence between the roof and floor in th e goaf was only 20 mm and the max ground surface subsidence related to the coal mining face was 5 mm.