Method for preparing an ashfree coal including a devulcanizing step

The invention discloses a method for preparing an ashfree coal, comprising the following steps: (A) mixing a raw coal with a solvent in a preset rate to form a slurry; (B) placing the slurry into an ultrasonic extraction reactor and making the slurry react using the ultrasonic wave so as to dissolve the organic component in the raw coal by the solvent and then separate the slurry into a dissolved organic component and a not-dissolved particle matter; (C) devulcanizing the dissolved organic component to remove the sulfur compound; and (D) drying the devulcanized organic component. According to the invention, the ashfree coal with very small amount of the ash content (0.01-0.2%) is prepared and the yield of the organic component extracted from the coal is increased and the ash yield of the ashfree coal is reduced. In the method for preparing the ashfree coal, the content of the sulfur in the ashfree coal is reduced by below 50% without extra energy consumption.