Abstract: Presented in this paper is a one-dimensional computational model for numerical simulation of migration process of pollutants in waste landfills which can take both the sorption of aquifer and bio-degradation of wastes into consideration. The model, for the case of a clay liner of finite depth, can simulate the complex migration mechanisms including advection and dispersion transport as well as geochemical reaction. Based on the computational model, numerical solutions are achieved by using semi-analytical procedure. Then through comparative parametric studies, the key factors which considerably control the migration process of containments are defined based on the numerical results. It is shown that for most practical situations the concentration of contaminant within the groundwater beneath landfill will gain its peak value at a specific time and subsequently will decrease with time. It is found that the most important factors affecting the migration process of pollutants include the thickness and permeability of the clay liner, sorption capacities of both aquifer and clay liner.