A system for testing a DC power supply performance includes a comparison module, a judge module, and an alarm module. The comparison module receives DC voltage signals from the DC power supply, compares the DC voltage signals with a reference voltage respectively, and outputs a voltage level signal when the DC power supply is normal. The judge module receives the voltage level signal, and outputs a control signal according to the voltage level signal. The alarm module receives the control signal, and indicates status of the DC power supply according to the control signal.