Abstract: In order to effectively reduce the water content of residual sludge in the municipal wastewater treatment plants, the performance of sludge dewatering by acid-heat (temperature < 100℃) treatment processes was evaluated. The effects of pH, temperature, and heating time on sludge dewatering were studied. Meanwhile, the mechanism of sludge dewatering was tentatively elucidated based on the soluble chemical oxygen demand (SCOD), protein and polysaccharide in the sludge supernatant, zeta potential analysis, and floc morphology of the sludge. The results showed that: (1) The SCOD of sludge supernatant increased to 925.76 mg/L after the sludge was treated by acid-heat treatment for 40 min, indicating that the extracellular polymeric substances (EPS) of sludge could be effectively broken with the release of the internal bound water. (2) The zeta potential of raw sludge was -14.10 mV, it decreased to -3.49 mV after acid-low heat treatment, and the electrostatic repulsion between sludge particles decreased significantly. (3) The combined treatment process of acidification and low temperature heating was beneficial to the flocculation of sludge since large and compact flocs were formed, suggesting that the dewatering performance of sludge was improved. (4) The optimal treatment conditions were determined as follows: pH 3, temperature 90℃ and heating time 40 min. Under such conditions, the sludge dewatering rate could reach 20.67 mL/min and the moisture content of cake was reduced to 63.05%. In conclusion, the combined treatment process can effectively improve the sludge dewatering performance and release more dissolved organic matter under low temperature heating conditions. The moisture content of the sludge can be reduced to nearly 60% after filtration, which is a feasible sludge dewatering method.