Abstract: : In order to address the global climate change, China has announced the decision to increase its nationally determined contributions and implement more effective policies and actions to reach carbon peaking and carbon neutrality. Construction, operation and maintenance of tunnel projects will generate huge amount of carbon emission, so accurate quantitative analysis and assessment of carbon emission will be important for achieving the dual carbon goals. The tunnel carbon emission boundary has been identified by using the LCA method, and the carbon emission calculation model for the full life cycle of tunnels has been established. Based on an actual project, the carbon emission in the full life cycle of tunnels has been calculated and assessed. According to the results, the carbon emission in the tunnel construction stage is mainly generated by materials production, and the carbon emission in the O&M period is closely related to the tunnel length. Based on the energy consumption proportion of the lighting section of the tunnels of various lengths, it is deduced that the proportion of lighting induced carbon emission in the middle section of tunnel increases as the tunnel length increases. The lighting design of tunnel is related to the traffic volume, so an uncertainty analysis of tunnel lighting energy consumption has been conducted by using the particle swarm optimization, with the traffic volume variation taken into account. As the results indicate, in a 500~4 000 m long tunnel, the carbon emission generated by the lighting energy consumption in the entrance section zone takes a significant proportion in the lighting section and this means great potential of energy conservation and emission reduction.