This paper describes desulfurization characteristics of low sulfur coals prior to combustion and optimum conditions of three different desulfurization processes. These processes include two thermal treatment processes (mild pyrolysis and air oxidation) and an H₂O₂ leaching process. Dual processes composed of thermal and leaching processes were also evaluated. Low sulfur coals employed were two imported bituminous coals and two domestic anthracite coals. The optimum reaction temperatures and times of the thermal processes were 500-550 ℃ and 15-20 minutes, respectively. The optimum condition for the leaching process was obtained when the experiment carried out for 60 min at 90 ℃ using 30% H₂O₂. The dual process showed the best sulfur removal efficiency as expected among the evaluated processes.