During hydrothermal treatment (HT) of sewage sludge (SS), its cell structure is decomposed and its organic content is released. An increase in the total organic carbon content in the liquid phase was experimentally determined in the temperature range of 130-250 oC with a fixed pressure of 5MPa and residence time of 10min. By using the Arrhenius equation, the pre-exponential factor and activation energy were successfully determined for the first time for the degradation of SS cells as 3.96×1010 s1 and 115 kJ mol1, respectively, for the temperature range of 130-250 oC. Increasing the HT temperature increasingly destroyed the cell structure of SS. Keywords:Hydrothermal Treatment, Sewage Sludge, Total Organic Carbon, Cell Structure