Abstract: The large-scale construction activities and operation of urban metro consumes huge quantity of resources and energy, which has gradually become a major contribution to the environmental impact of the urban transportation sector. Taking Shenzhen as a case, this paper evaluated the resource and energy consumption intensities of metros' construction stage by using life cycle assessment(LCA) method. The global warming potential(GWP), measured by CO₂ equivalent, was chosen as the impact indicator to build a carbon emission calculation model of metro's construction phase. Meanwhile, scenarios-based analysis was adopted to predict the emission reduction potentials. The results showed that the cumulative carbon emission caused by the construction of metro lines and stations in Shenzhen city reached approximately 27.3 million tons of CO₂e by 2020, of which 72% from the stations' construction, and 28% from the tunnels construction. Specifically, the carbon emission intensities of shield tunnels and stations were approximately 13000 tons CO₂ e/km and 371.2 tons CO₂ e/100 m², respectively. In addition, the carbon emission reduction rate of metros' construction reached 8.5% annually, or an accumulative amount of 5.08 million tons from 2021 to 2035, if green technologies adopted, such as the use of recycled concrete and recycled steel. And that can probably significantly alleviate the carbon emission of metros' construction.