Abstract: In order to explore the differences of carbon emission between two common construction methods, i. e. shield method and drill and blast method, the construction of some tunnel sections of Shenzhen Metro Line 7 is taken as an example to calculate, by using the carbon emission calculation formula, the carbon emission intensities and contribution ratios of the key emission sources of the two methods in the three stages, i.e. construction materials production, costruction materials transportation and onsite construction. According to the calculation results, the average carbon emission intensity of the shield method is 8,104.4 t CO2eq/km and that of the drill and blast method is 15,124.8 t CO2eq/km, so the carbon emission of the shield method is less. In both methods, the carbon emission in the construction materials production stage exceeds 80% of the total carbon emission. Steel, concrete and cement are the key sources of carbon emission. The contribution ratios of the three construction materials in carbon emission are 40%, 1.1% and 47% in one tunnel construction method and 39%, 29% and 26% in the other. By optimizing or improving the construction material production processes or increasing the proportion of clean energy in electric energy structure, the carbon emission factors in construction materials production and electric energy production can be reduced, to eventually reduce carbon emission significantly.