As an important link and bridge for emission reduction, power grid companies are more willing to build clean power transmission and transformation projects under the “3060” carbon emission target. With this problem at its core, this paper uses a typical 220 kV line and substation in a province as the case data. This study improves the carbon emission measurement method for the entire lifecycle of power transmission and transformation equipment, compiles and summarizes the carbon emission coefficients of each equipment and duration according to different typical scenarios, and measures the carbon emission of power transmission and transformation projects. The results show that the carbon emission of the line is 8169.58 tons, mainly concentrated in materials such as steel, water, concrete, and cement; the carbon emission of the substation is 4483.48 tons, mainly concentrated in materials such as concrete, cement and steel; and the carbon emission of the operation and maintenance stage is 9939.70 tons. The carbon emission coefficient in this paper can be extended to all the carbon emission accounting of power transmission and transformation projects in China.