Abstract: Tests the tube of the heater and analyzes the reason of tube's corrosion resulting from high temperature oxidation, in form of homogeneous sheet, and partial corrosion resulting from acidic matter deposition. A difference between a minimum value from heater's actual test value and an allowed value from tube calculation is utilized to determine the degree of tube's corrosion. It is considered that acidic corrosion takes up a great proportion in heaters, especially in square chest furnaces. It is proposed to strengthen regularly dust and coke cleaning treatment, make dry maintenance to the heaters unused for a long time and improve heater's combustion property.