Abstract: With the development of social industrialization，the problem of water pollution is prominent. Many water plants at home and abroad use biological activated carbon (BAC) to remove trace organic pollutants in water， but they need to be regenerated after a certain period of time，among which thermal regeneration is a method of activa⁃ ted carbon regeneration that is most widely used in the industry. In order to conduct a comprehensive study on the py⁃ rolysis characteristics of spent biological activated carbon (SBAC) which is in water treatment during thermal regener⁃ ation，the method of comparing the fresh activated carbon (FAC) with spent activated carbon of adsorption a single substance of phenol (hereinafter referred to as AC⁃P) was employed，through the experiment of combining thermo⁃ gravimetry and fourier⁃transform infrared spectrometer (TG⁃FTIR)，the weightlessness，heat absorption and release as well as gaseous product of three of them were contrasted and analyzed; besides，the pore structure of spent activa⁃ ted carbon pyrolyzed at different temperatures was characterized by the value of iodine and methylene blue to deter⁃ mine the optimal regeneration temperature of the SBAC. According to the research，it is concluded that during the py⁃ rolysis，SBAC mainly indicates physical desorption of water and volatile organic matter under 40-360 °C，it indicates pyrolysis of easy⁃pyrolysis organic matter under 360-772 °C，under 772-885 °C，the pyrolysis of organic matters basi⁃ cally ends，and weight loss under 885-1 200 °C is relatively small，which mainly indicates the thermal reaction of raw materials and slow decomposition and carbonization of high carbon residue; pyrolysis will happen to biologi⁃ cal membrane during thermal regeneration. According to the value of iodine and methylene blue，the pores of SBAC re⁃ covered gradually when the regeneration temperature reached 300 °C ，and the value of iodine and methylene blue in⁃ creased rapidly from 500 °C ，and the value of iodine slows down after 700 °C . The value of iodine and methylene blue reached the maximum at 850 °C ，and then the value of iodine and methylene blue decreased due to the further deposi⁃ tion of fixed carbon in the activated carbon pores. Therefore，the optimal the optimal temperature for pyrolysis and re⁃ generation of SBAC is 850 °C . This research gives a comprehensive analysis on the pyrolysis characteristics of spen