Abstract: The 1 000kV extra-high voltage electricity transmission and transformation project is one of most important projects in the services of interregional electricity supply. The extra-high voltage substation will obviously impact the outside acoustic environment by the running of transformers and reactors and other facilities. Therefore, it is necessary to take measures to reduce the noise impact on the outside acoustic environment in project design phase. Applying frequently-used techniques of acoustic insulation in large substations and converter stations, three schemes were programmed with Cadna/A to find out effects of noise reduction by the simulation of the acoustic environment outside and inside the substation. The results showed that in normal conditions, the distance of station boundary noise exceeding the standard limits would be over 200m, the project would cause nighttime noises of neighboring village to increase obviously, and the impacted neighboring area was more than 301 000 m². If the reactors added the Box-in structure, the restricted land area exceeding the standard limit outside the substation would decrease by more than 75%. When both the transformers and reactors used the Box-in structure, the boundary noise of extra-high voltage substation could meet the standard, and the increment of nighttime noise in neighboring villages was less than 1 dB(A).