Abstract: Facing the fact of less understanding about the function of the covering layer，the relationship among the thickness of covering layer，mining process，loss and dilution，water prevention and drainage and mine ventilation are discussed through experiments.Results show that the thickness of covering layer have a greater impact on the drawing shape，ore recovery rate present a parabolic adding rule as the thickness increases.The infiltration coefficient show different on each layer，and the relative location of the layer which mentioned to prevent water and air moves down.Finally，based on analysis of the design parameters of the on-site mine，the thickness of covering layer for Shouyun Iron Mine was optimized with the results above to obtain a reasonable thickness of covering layer.

Key words: Transferring from open pit into underground mining, Thickness of covering layer, Loss and dilution, Infiltration law, Features of air leakage