The construction of UHV AC projects has significant advantages in improving the clean energy consumption capacity and optimizing the large-scale allocation of energy resources. At present, the carbon emission reduction benefits of UHV AC projects have not been quantitatively studied, and equipment transportation is an important part of UHV AC project construction. Based on this, the paper determines the boundary of carbon emission accounting system in the equipment transportation stage, clarifies the key factors of carbon emission reduction in this stage, and proposes carbon emission accounting methods. Through the analysis of an actual project, the results show that the equipment transportation link can reduce carbon emissions and improve the carbon reduction benefits of ultra-high voltage AC projects by optimizing the transportation path and mode.