The secondary circuit of smart substation is based on SCD, which includes a merging unit, an intelligent terminal, as well as a switch, etc. There is a tendency to implementing process level device at the switchyard, and it means inconvenient to test relay system for maintenance issue. In order to improve the efficiency of site routine test, IEC 61850 based test mode is developed, a new method of “non-intruding test” to test relay system is proposed based on network test case, with which it is not necessary to disconnect fiber and adjust setting on site. Under this circumstances, the test procedure will be improved rapidly and furthermore it can prove the unique benefit of smart substation compared to conventional substation.