The invention discloses a test system and method for a transformer substation secondary device prefabricated cabin. The system comprises an integrated test platform, an optical fiber interface, a test work station, a switch device, an IEC61850 network message analyzer and a transformer substation secondary device prefabricated cabin being tested. The integrated test platform is connected with the transformer substation secondary device prefabricated cabin being tested via the optical fiber interface, the transformer substation secondary device prefabricated cabin being tested is connected with the IEC61850 network message analyzer via the switch device, and the integrated test platform is also connected with the IEC61850 network message analyzer via the test work station. The test system and method can accurately, reliably and rapidly realize high-efficiency testing of the transformer substation secondary device prefabricated cabin, a problem that a secondary device prefabricated cabin is small in internal size and insufficient in testing methods can be addressed, requirements for large scale construction tests for the purpose of modularized construction of transformer substations can be met, test efficiency is improved and the test system and method have good application prospects.