The worldwide increase in amount of sewage sludge has recently attracted considerable interest in developing an efficient and economical sludge disposal method. A sewage sludge treatment process combining the hydro thermal treatment (HT) of sludge and the catalytic hydrothermal gasification (CHTG) of its derived liquid (HT& CHTG-Process) is proposed in this paper. Liquid hourly space velocity (LHSV) value of 25-100 h(-1) and liquid flow rate of 10-40 mL/min were employed with a self-designed CHTG experimental setup. During the first stage of the HT-Process, approximately 56% of the carbon in the sludge was transferred into the derived liquid at 300 degrees C, During the second stage of the CHTG-Process, the derived liquid was gasified into CH4, H-2, and CO2 using a Ni/carbon catalyst, and the carbon conversion reached 88% at 350 degrees C and 20 MPa with a LHSV of 25 h(-1). Using the integrated HT&CHGT-Process, approximately 0.78 Nm(3) of CH4, 0.62 Nm(3) of H-2 and 0.31 Nm(3) of CO2 were generated from 1 kg of carbon in the sewage sludge. The combined process was expected to be an efficient method for sewage sludge treatment due to its mild conditions <= 350 degrees C and <= 20 MPa) and high yield of fuel gases.