A method for determining breakthrough time of anti-seepage liners in a landfill, includes (a) detecting a leachate sample of the landfill to determine the initial concentration C0 of pollutants, and monitoring the leachate head h of the landfill; (b) determining the pollution-causing concentration CA of the pollutants according to functional orientation of local groundwater of the landfill; (c) determining, related parameters of the anti-seepage liners including the thickness z of the anti-seepage liners, the permeability coefficient k of the liners, and the porosity n of the material of the liners, and determining the related parameters of pollutant migration including the effective diffusion coefficient Da* and the mechanical dispersion coefficient Dm of the pollutants in the anti-seepage liners, and the adsorption retardation factor Rd of the anti-seepage liners on the pollutants; and (d) calculating the breakthrough time t of the anti-seepage liners according to a formula, t = nR d ⁢ z 2 ( h + z ) ⁢ k ⁢ ( ( a ⁡ ( C 0 C A ) b ) ⁢ ln ⁡ ( ( h + z ) ⁢ k n ⁡ ( D a * + D m ) ) + c ) .