The large-scale transportation infrastructure construction in developing countries such as China requires emission estimation method for better project design. This study proposed an empirical method to estimate carbon dioxide (CO₂) emission which was generated from highway construction based on four real projects in southwest region of China. The proposed method estimated the total emission from different steps of construction process (raw material production, material transportation and onsite construction) by different project types (e.g. subgrade, pavement, bridge, and tunnels). The results show that in general over 80 percent of the CO₂ emission was generated from raw material production; the onsite construction and material transportation only accounted for 10 and 3 percent of the whole CO₂ emission, respectively. Moreover, the CO₂ emission from bridge and tunnel constructions was much larger than subgrade and pavement construction. The total CO₂ emission from road, bridge and tunnel constructions was 5229 kg/m, 35,547 kg/m and 42,302 kg/m, respectively. The empirical estimation method of the CO₂ emission proposed in this study can be considered as references for CO₂ emission estimation in other regions which are similar as southwest region of China.