Abstract: In order to investigate the influences of the attenuating characteristics of reaction parameters including adsorption and degradation in the clay liners under the geomembrane on the antifouling performances of composite liners, the attenuation of reaction parameters is expressed as a specific function. The one-dimensional semi-analytical solution for transport of organic contaminants in composite liners is obtained by the Laplace transformation. The semi-analytical model is validated through the field test data. The results of dimensionless analysis show that when the reaction parameters in CCL decrease rapidly with the increase of depth (e.g, β=0.1), the breakthrough time can be reduced by 68%. The bottom concentrations and fluxes can be reduced by 40% when the diffusion and degradation dominate transport of contaminants (e.g., Pe₂≤1 and Q≥10). The attenuation effects of the reaction parameters can be ignored when the advection is the dominant process (e.g., Pe₂≥10 and Q≤1). Without considering the attenuation of reaction parameters, the breakthrough concentration of hydrophilic organic contaminants and hydrophobic organic contaminants can be underestimated by 61% and 37% respectively. The field monitoring data can be better fitted by the proposed model, and it can be used to evaluate the effectiveness of landfill liners. It can also be used for the design of composite liners and the verification of complex numerical models.