Abstract: In consideration of the change of physical and mechanical properties of waste body with the time and the degree of degradation， the landfill was divided into five different degradation areas， different cohesions and internal friction angles were specified in order to study the influence of the biodegradation of waste body on landfill slope stability. The safety factor of the landfill site was calculated using FLAC3D， and the failure mechanism of landfill slope stability was analyzed. The landfill slope stability was examined through a couple of instances， and the calculation result of the numerical method is lower than the result with the limit equilibrium method. This method can predict the local bucking failure of landfill under complex boundary conditions and the failure caused by extremely big displacement of slope. And it should be more useful for the analysis of the stressstrain failure mechanism.

Key words: landfill, slope stability, biodegradation, FLAC3D, finite difference method.