Abstract: Through researching on the permeability rules of back fillings in upper horizontal sublevel sandfill mining，a mathematical model for obtaining fillings dehydration time under various influences involving permeability coefficient，storage coefficient，thickness of back fill and the space of dehydration wells is established，then the homologous numerical program is complied with MATLAB.After then，the testing theory and methods in accurately predicting the coefficients of permeability and storage in laboratory are proposeed.On this basis，the numerical simulation for dehydration efficiency in the upper horizontal sublevel sandfill mining of Hongtoushan copper mine under different technical parameters is carried out，achieving the relationship curve between each parameter and the dehydration efficiency.

Key words: Sandfill mining, Filling materials, Permeability coefficient, Storage coefficient