By the two methods that PVD sputtering and PVD sputtering associated with electroplating，the different thickness Fe-C alloy films on fiber core were made. X-ray diffraction results show that the Fe-C alloy films have the same crystal structure as ordinary steel. In order to carry on the corrosion experiments, putting the galvanized fiber into different concentration HNO3 solutions and concrete block respectively. The results show that: In low concentration etching solution, the different thickness Fe-C alloy films can be eroded from outside to inside evenly:,and the output optical power increases suddenly in the corrosion last stage;In highly concentrated etching solution, the Fe-C alloy films produce the crack in many parts, the films are perished piece by piece, and the output optical power increases gradually in the mass;In the corrosion experiment which was made in a concrete block, the change of the output optical power is complicated, but in the whole it is increased.