The invention relates to an anode-cathode device for on-site metallurgical-phase electrolytic polishing corrosion instruments. The device comprises a power source, an anode assembly and a cathode assembly, wherein the anode assembly is connected with a positive pole circuit of the power source and fixedly arranged on a large-size workpiece, and is a certain distance away from the metallurgical examination site; the cathode assembly is connected with a negative pole circuit of the power source, and contacts the metallurgical examination site on the large-size workpiece after absorbing a chemical polishing reagent; and after the power is on, the device can perform electrolytic polishing corrosion on the metallurgical examination site. The invention also relates to an application method of the anode-cathode device for on-site metallurgical-phase electrolytic polishing corrosion instruments. The cathode assembly is used for absorbing the electrolytic chemical reagent; and thus, when the metallurgical examination site is subjected to polishing corrosion, the electrolytic chemical reagent can sufficiently contact the metallurgical examination site, and the anode assembly can be fixed to the ferromagnetic or non-ferromagnetic large-size workpiece, thereby implementing the metallurgical test on the metallurgical examination site on the on-site large-size workpiece by using the metallurgical-phase electrolytic polishing corrosion instrument, and achieving favorable polishing corrosion effects.