Pipes serving for water distribution system for different years in northern city, were chosen as objectives for study.The shape and component of corrosion scales were measured, and formation mechanism of corrosion was also analyzed.The corrosion mechanism of pipes was studied on the sides of electrochemistry and microbe.The solution to eliminate corrosion scales in water distribution system was also proposed.The results show that the specific surface areas of five corrosion scales are between 41.35 and 132.3 m2/g and the dimension of corrosion scales enlarge with the increase of serving age, which could induce the decrease of water flow cross-section.