The construction of highways involves significant material consumption and a complex construction process, resulting in substantial carbon dioxide emissions. To calculate the magnitude and intensity of CO2 emissions during construction phase, an accounting model was developed based on the theoretical foundation of life cycle assessment (LCA), engineering materials consumption quotas, emission coefficient method. This model was applied to assess the emissions of a newly constructed highway in China, enabling identification of carbon emission characteristics across different stages and projects during the construction period. The findings indicate that: 1) total carbon dioxide emissions during highway construction amount to 1,092,026 tons with an emission intensity of 3722 tons/km-lane; 2) materials stage accounts for 93.79% of carbon emissions while transportation and off-road machinery stages contribute only 0.75% and 5.46%; 3) among various unit projects, intersection, subgrade, pavement, bridge projects exhibit higher levels of carbon emissions compared to others which can be disregarded due to their negligible contributions. Additionally, both engineering materials and construction machinery follow the similar Pareto Principle regarding their respective contributions to overall emissions patterns. Therefore, to mitigate carbon emissions during the highway construction phase, particular attention should be directed towards the materialization stage where emissions are primarily concentrated. From an operational control perspective, transport industry and construction entities ought to implement measures targeting material production and fossil fuel extraction stages as well as fossil fuel combustion stage respectively, with the aim of reducing overall carbon emissions throughout the construction process.