The lining layer of the simple landfill site is compacted clay. determines The life of landfill is directly determined by the permeability of the lining layer. The puncture depth of leachate and getting the economic and safety thickness were calculated by determining leachate ’ s rate and scope in the clay. Based on the homogenization theory, the analysis model was established by the use of finite element software. At last the size effects of backfilling clay in landfill was analyzed. Results show that the lining of the permeability decreased with the decrease of the piece of diameter size, meanwhile, the life of usage of landfill increased.