The electrochemical corrosion affects soft-magnetic properties and service life of amorphous or nanocrystalline Fe73.5Si13.5B9Nb3Cu1 alloys. Therefore it is important to characterize the corrosion characteristic of the alloys for their potential application to engineering fields and further alloy development. In this study, the corrosion behavior of nanocrystalline Fe73.5Si13.5B9Nb3Cu1 alloys prepared by crystallization from the amorphous state was studied and compared with that of their amorphous counterparts by linear polarization (PLZ) and electrochemical impedance spectroscopy (EIS) technique. In electrolyte of 0.01 M NaCl, annealing at 550 °C leads to the decreased corrosion rate, while crystallization at 650 °C gives rise to the increase of corrosion rate. In the blend solution of 0.1 M NaCl and 0.1 M NaOH, heat-treatment at 550 °C or 650 °C improves the corrosion resistance for the alloys.