In the context of the world facing environmental, economic, and social challenges, sustainable development is not only an option but also an urgent task for the construction industry. The goal of reducing emissions from construction activities is the first step to implementing environmentally sustainable construction activities. To achieve this goal, it is necessary to reliably estimate emissions from construction equipment, which accounts for the largest proportion of the total impact of construction activities. However, it is challenging to assess the environmental impact accurately from the perspective of equipment operation at the planning stage due to the lack of suitable methodologies. This study presents a method to quantify emissions from construction machinery using a discrete event simulation (DES) technique, namely EZStrobe. A case study involving digging and earthmoving activities in an airport construction project in Vietnam is conducted. Emission factors are integrated into the DES model to quantify emissions. Furthermore, the equipment fleet is optimized to minimize emissions through the analysis of simulation scenarios, combined with the consideration of factors such as time, productivity, and fuel consumption. The comparison with the real case showed that CO2 emissions and fuel consumption were reduced by 7,9% and 8,6%, respectively. Air pollutant emissions such as NOx, HC, CO, and PM are reduced by 9%, 6.8%, 10,1%, and 6.4%, respectively. In addition, the optimized scenario improved construction productivity by 47.5%. DES tool aids construction planners in identifying potential opportunities to reduce emissions and move toward sustainable construction.