Bridges are the main source of carbon emissions from highway construction, and the carbon emissions of different types of bridges vary greatly. This study applies the carbon emission accounting theory of life cycle evaluation and the emission factor method to measure the carbon emissions during the construction period of bridges along a highway in Guangzhou, analyses the results and characteristic of carbon emissions of different structures according to the sub-projects, analyses the intensity value of carbon emissions of the major structures of bridges and establishes an estimation model of carbon emissions by taking the quantity of engineering and the length of bridges as the influencing factors. Through the calculation and analysis, it can be seen that the carbon emission of the upper structure of the bridge accounts for the highest proportion, accounting for more than 42%. Calculations show that the carbon emissions per kilometre of cast-in-place concrete steel bridges are much higher than those of other types of bridges, and the carbon emissions per m3 of different superstructures are the highest for steel box girder structures.