Abstract: One-dimensional mathematical model for diffusion of organic contaminant through GM+GCL+AL composite liner is developed to investigate the behavior of organic contaminant transport in GM+GCL+AL composite liner. The diffusion of organic contaminant through GM is assumed to be a steady-state process. The analytical solution for the model is obtained. The results obtained by the proposed analytical solution are in good agreement with the previous analytical solutions. The effect of degradation in AL the diffusion of on organic contaminant is investigated on the basis of the proposed model. The equivalence between GM+GCL+AL and GM+CCL is discussed. The bottom flux of the GM+GCL+AL composite liner is reduced when the thickness of AL increases. The standard GM+0.75 m CCL can be replaced by a combination of a GM, a GCL and a more than 2 m thick AL under the proposed conditions.