Field tests are conducted on the electronic transformers in Sunan 500 kV UPFC project in order to examine their performance.Test equipment and method are presented referring to DC accuracy test and transient step test.A signal source is employed to produce primary current signal as the input of transformers to be tested and the standard transformer.A transformer tester is applied to receive the output signals of the two which are compared and analyzed accordingly.Test results show that performance of the transformers utilized in the project meet the requirements of operation.In addition,the test verifies the practicability of the equipment and the method.It can provide reference for further tests on the transformers.