Abstract: In order to decrease the sulfur content, chemical desulfurization tests were conducted by alkali treatment. The effect of alkali type, mass concentration of NaOH, reaction temperature, reaction time, pretreatment temperature and coal particle size on the desulfurization was investigated, and the mechanism of desulfurization was preliminary studied. The effects of pretreatment temperature, mass concentration of NaOH and coal particle size on desulfurization were examined by the orthogonal test, and the better levels of factors were determined and optimized. Under the conditions that in ordinary pressure, pretreatment temperature is 200 ℃, mass concentration of NaOH is 15 g/mL, and the coal particle size is less than 0.074 mm, the sulfur content can be reduced from 6.91% of raw coal to 2.43% of refined coal, the desulfurization rate can be up to 64.83%, and ash content can be reduced to 11.73%.