The disclosure discloses a light emitting diode testing apparatus, which includes a power supply module, a probe, a control unit and a data acquisition unit. The power supply module provides a first current or a second current to a testing item. The probe measures characteristics of the testing item. The control unit controls the power supply module to provide the first current or the second current. The data acquisition unit acquires the characteristics of the testing item from the probe. The power supply module includes a first current source, at least one second current source and at least one protector. The first current source provides the first current to the testing item. The at least one second current source provides at least one additional current. The at least one protector prevents the first current from feeding back to the at least one second current source.