The corrosion behavior of galvanized flat steel, which has been used for more than eleven years in the soil environment, is investigated by using optical microscopy, scanning electron microscopy, and X-ray diffraction techniques. It is found that the corrosion type of galvanized flat steel is mainly general corrosion after buried in soil. The corrosion products are composed of FeOOH, Fe₃O₄ and others. The EDS results show that there are some sulfur elements in the corrosion product, and the elements might be caused by the sulfate-reducing bacteria. Also there are some Al-Si composite granular inclusions existing in the substrate of galvanized steel, and the inclusions could promote the corrosion occurrence and development, therefore provide the channel for the corrosive ion to permeate into matrix in the local region. In order to extend the lifespan of grounding electrode in the soil, the galvanized steel is often considered in the design. The zinc in the soil is priority eroded to protect ordinary carbon steel's lifespan. In the absence of current role, the service lifespan of galvanized steel is indeed better. However, due to the role of the ground current, as the ground material, galvanized steel surface electrolytic zinc coating will soon come off; then the corrosion rate of grounding electrode accelerates rapidly. The conclusions also indicate that in the corrosive soil environment, the corrosion and failure of galvanized flat steel could affect the function and lifespan of grid.