The moisture distribution and thermal drying characteristics of dewatered sludge in anaerobic digestion were investigated by a thermo-gravimetric analyzer (TG) and the isothermal kinetic characteristics during the drying were developed by an unreacted core model. The TG results showed that the bound water was partly converted to the free water with the invariant interstitial water and surface water after anaerobic digestion, which enhanced the drying performance of sludge. The time required for the complete drying of digestate was less than that of the raw sludge in the same temperature. The moisture evaporative efficiency of digestate was related to the vapor diffusion rate of the outer surface, and the drying efficiency of digested sludge cannot be enhanced by increased temperatures.