Fully understanding the corrosion damage characteristics of the secondary loop pipeline plays an important role in ensuring the safe, stable and economic operation of a nuclear power plant. flow accelerated corrosion(FAC), erosion corrosion(EC), high temperature corrosion(HTC) and under insulation corrosion(UIC) are the main corrosion damage forms of secondary loop pipeline. The damage characteristics of FAC in liquid single-phase flow and vapor-liquid two-phase flow are obviously different. Under specific operating conditions, different EC damages such as flash evaporation, droplet impact, HTC erosion, cavitation corrosion, jet cutting, etc may occur. In this paper, the formation conditions, damage morphology, wall thickness distribution, thinning rate and other characteristics of corrosion damage of secondary loop pipeline in nuclear power plant are compared and analyzed. On this basis, these corrosion damages of the secondary loop pipeline in nuclear power plant could be effectively identified and targeted managed.