The invention discloses a system and a method utilizing low-tank coal. The system comprises a pyrolysis unit, a desulfuration and decarburization unit, a sulfur recovering unit, a catalyst preparing unit and a pyrolysis oil gas processing unit, wherein the pyrolysis unit is used for pyrolyzing low-tank coal dust, filtering and cooling pyrolyzed oil gas and separating an oil-water mixture; the desulfuration and decarburization unit is used for performing desulfuration and decarburization processing on gas to obtain a product gas; the sulfur recovering unit is used for recovering hydrogen sulfide in acid gas after desulfuration and decarburization, and hydrogen sulfide is further converted into elemental sulfur; for the catalyst preparing unit, a desulfuration adsorbent is used for adsorbing the acid gas, and the adsorbent after saturation by adsorption is used as the catalyst for the pyrolysis oil gas processing unit; and the pyrolysis oil gas processing unit is used for reaction of hydrogen, the catalyst and coal tar. The system and the method can sufficiently utilize acid gas produced during coal pyrolysis and tar hydrogenation, and can complete the preparation of a coal tar suspended bed hydrogenation pretreatment catalyst while processing the acid gas with the adsorbent.