Abstract: Corrosion is a serious threat to the safe and stable operation of coal-fired power plant boilers. A typical pitting corrosion failure case was introduced, and by analyzing the macro and micro morphology of the water-cooled evaporation wall SA-210C seamless steel tube and chemical compositions and microstructure of the corrosion products, the cause of the leakage was concluded to be pitting corrosion of the tube, which was caused by the unreasonable treatment process of the boiler water. The corresponding corrective measures were proposed to avoid the recurrence of such problem.