Abstract: Landfill is the common way to treat the municipal garbage at present. However, the leachate from the landfill is the main source of groundwater pollution. In this paper, a municipal landfill in Shanghai City is selected to study the effects on groundwater. Seven monitoring wells are set up in the field around the landfill site. The groundwater quality in the area was monitored for two years before and after the landfill. The water samples were taken as the background before landfill to evaluate the groundwater quality by using Background Method. The results show that the groundwater quality of the whole area is in a steady state. It is not affected by the leachate from the landfill up to now, although there is a great change in the water quality of individual monitoring wells. The reason is that the lid of monitoring well was destroyed in the construction process, and the wellhead directly exposed to the external environment. With continuous landfill operation, the effects of leachate from the landfill on groundwater remain for future studies.