Anti-seepage method for open mining pit

The invention relates to an anti-seepage method for an open mining pit, and solves the problem that catchment water cannot be prevented from entering the mining pit through surface water seepage around a realm by a common water interception and drainage method. Before or after stripping of a mining pit is started, sundries around the boundary of the mining pit are removed, surface soil with the thickness of H2 + H3 is stripped in advance in the inclined direction outside the pit at the transverse gradient of 1%-3%, then an annular waterproof reverse slope section with the thickness of H2 + H3 and the inclined transverse gradient of 1%-3% towards the outside of the pit is constructed, H3 is the thickness of a clay impermeable layer, and H4 is the thickness of a clay impermeable layer. The clay impermeable layer is formed by compacting clay with low permeability and high compaction rate selected from the periphery or in a pit, H2 is the thickness of the rain wash resistant layer, the rain wash resistant layer i