Abstract: Perforation failure occurred in the copper pipes for cooling tower in use. The water, copper pipes and filth product were analyzed, and the results showed that the main failure reason was the excessive amounts of chloride ions in circulating water because of the improper maintenance. The failure was the result of electrochemical corrosion and chemical etching, and electrochemical corrosion was the main reason. The electrochemical corrosion occurred because of the excessive amounts of chloride ions and soluble salt promoted the hole corrosion.