Abstract: Large tube type fuel heating furnaces are important and essential equipments, which have a wide range of applications in the petroleum and chemical industry, and failure modes of the furnace tubes in them are mostly caused by carburizing. It is important to improve effective detection technology for the measurement of the tube carburized layer thickness, as well as the research on the comprehensive performance of furnace tubes considering the impacts of different conditions. The cracking furnace tube of  70 mm×6 mm HP40Nb specifications was studied to evaluate the effectiveness of an acoustic emission(AE) technique, which used to measure the carburized layer thickness. In experiment, different carburizing time factors were mainly taking into account, and the response of acoustic emission attenuation to the organization changes, the magnetic field changes, and additional stress which caused by carburization are considered. The results show that the short periods strong carburizing has obviously impacts on the changes of the organization and magnetic field of the cracking furnace tube. It however, has little contribution to the acoustic emission signal attenuation.