Abstract: Water wall tube of gasifier in a coal gasification company burst frequently during operation. The causes of bursting on tube were analyzed by means of chemical composition analysis, metallographic examination and energy spectrum analysis, combined with the operation condition of gasifier. The results show that the main cause of bursting on water wall tube was that the circulating water flow in the tube was too low and the furnace temperature was too high, which made the water wall tube in a high temperature state, resulted in the spheroidization of pearlite in microstructure of tube wall and the decrease of material strength, which led to the burst of water wall tube.