In order to calculate the carbon emission of distribution transformers in the whole life cycle and reduce the carbon emission level of power grid, this paper proposes a calculation method for carbon emission of distribution transformers based on the life cycle evaluation method, and uses this method to calculate the carbon emission of four common types of distribution transformers. The carbon emission reduction of grade 2 energy-efficient distribution transformers with typical capacity of 400kVA and 630kVA is compared with that of grade 3 energy-efficient distribution transformers. The calculation results show that the carbon emissions of distribution transformers account for more than 98% of the total carbon emissions of transformers. When the energy efficiency level of distribution transformers with the same capacity is increased from grade 3 to grade 2, The carbon emission of oil-immersed silicon steel core distribution transformer decreased by about 18%, and that of dry-type distribution transformer decreased by about 10%.