Abstract: Long urban metro tunnel will make some effects on groundwater environment during their operation. This paper analyses it with Beijing Metro 8(Northern Part of Period 2) as an example. A system of evaluation method is set up in this paper. The damming effect on groundwater environment is quantified based on some calculations. Some environmental and engineering problems are evaluated. The conclusions can give the scientific base for protecting groundwater environment and economizing the construction of this urban metro. In addition, this paper can be a good reference for other metro constructions and evaluation.