Abstract: As the large-scale construction of smart substation, the refurbishment and extension of smart substations become more and more. The state-of-art about the test of the refurbishment and extension of secondary system in smart substation is introduced and the problems and new needs are described. The new test process combined pre-test and on-site test is presented, and the new method about the test is discussed in detail from four aspects which are the configuration and verification of SCD file, the construction of virtual simulation and test platform, the pre-test and the join-test on-site. The security measure for the on-site test is also provided. At last, take the extension of line as an example and make analysis; it will be helpful to the test refurbishment and extension of secondary system in smart substation.