Embodiments of the present disclosure provide a server cabinet power backup system and a testing method thereof. In a self-test process of the power backup unit, the battery management module may be configured to: control the battery pack to supply power to the self-test resistor to discharge the battery pack, control the battery pack to be charged after the battery pack is discharged, and collect a charge and discharge parameter of the battery pack, and the battery management module may be further configured to: determine attenuation performance of the power backup unit according to the charge and discharge parameter of the battery pack.