Abstract: Burst accident occurred during the operation of water wall tube in a power plant, the causes of burst failure of the water wall tube were analyzed by means of macro analysis, chemical composition analysis, metallographic examination, mechanical property test and so on. The results show that the harmful substances in the high temperature flue gas and smoke cause corrosion of the outer wall of the water wall tube, and reduced the water wall thickness, which resulted in a serious reduction of anti internal pressure strength of the water wall tube and the burst happened.