Drying and incineration technology has gradually become an important disposal method for sludge in the central urban areas oflarge and medium-sized cities in China. Hydrothermal carbonization can improve the dewatering property of sludge, thereby reducing theenergy consumption of the system. However, there are few reports on the energy consumption analysis of hydrothermal and drying sludgepre-disposal process. In this article, the distribution of three-phase products and the organic components of hydrothermal liquid at hydrothermal temperatures from 200 ℃ to 260 ℃ were studied. Based on this, the energy-mass flow model of the hydrothermal and air-dryingsystem was established, and the impact of different hydrothermal conditions on system energy consumption was analyzed. Finally,the energy consumption with air-drying system, and the anaerobic fermentation as well as the air drying system was compared. It is found thatwhen the pressure inside the kettle is 8 MPa, the temperature of hydrothermal reaction is increased from 200 ℃ to 240 ℃ .The energy consumption of the hydrothermal reactor decreases from 184 kJ/ kg (sludge,the same below) to 161 kJ/ kg, mainly due to a significant decrease in the proportions of aromatic hydrocarbons and nitrogen-containing heterocyclic rings in the hydrothermal liquid. When the temperature rises to 260 ℃ , the energy consumption increases to 278 kJ/ kg due to the significant increase in the vapor phase fraction and the recovery of aromatic hydrocarbon mass. It is found that the energy consumption of hydrothermal reaction at 240 ℃ decreases with the increase of pressure due to the influence of the vapor phase fraction. The decreasing trend slows down rapidly after the pressure increases to4 MPa. The total energy consumption of the direct air drying system is 1 942 kJ/ kg when the drying air temperature is 110 ℃ . In the anaerobic digestion and drying system, due to the efficient heat recovery of biogas, the heat consumption is as low as 212 kJ/ kg at 10 days′ digestion time, and the total energy consumption is 984 kJ/ kg. As for the hydrothermal carbonization and drying system, due to the significant enhancement of the dewatering performance, the total energy consumption can be further reduced, and the energy consumption is597 kJ/ kg at a hydrothermal temperature of 240 ℃ . This paper provides basic data and theoretical basis for the selection and optimizationof pretreatment methods before sludge incineration independently or coupled combustion in coal-fired power stations.