Abstract: The chemical compositions, microstructure of waste heat boiler tube for acrylic plant and phase compositions of internal scale were studied, the fracture cause was analyzed. The results show that calcium sulfate in the water scaled in the inner surface of the furnace tube, leading heat transfer coefficient of the furnace tube to decrease and water flow insufficiently, which caused the creep expansion of furnace tubes and warming and oxidation of outside wall of furnace tube. Spheroidization and graphitization of pearlite of furnace tube material reduced the high temperature properties. External oxide layer deterioration and creep expansion can cause furnace tube to be thin and the internal furnace scaling to aggravate, finally cause the furnace tube to burst. The softened water and the rationalization proposals to upgrade the furnace tube had been put forward.