In order to study the catalysis of SO42-/ZrO2 solid acid for the liquefaction of coal, a series of SO42-/ZrO2 solid acids were synthesized by the method of precipitation-impregnation. The catalytic behaviours of the SO42-/ZrO2 solid acids for the hydro-liquefaction of Shenhua coal and model compounds, such as diphenylmethane, bibenzyl and phenyl ethyl ether, were investigated. In addition, non-catalytic liquefaction and the catalytic liquefaction under N-2 were further compared with the catalytic liquefaction under H-2 in order to understand the catalytic mechanism of SO42-/ZrO2 solid acid. The results indicate that hydro-liquefaction conversions of coal and model compounds are related to the strength, amount and nature of acid sites on the surface of SO42-/ZrO2, and the strong acid site responds to their catalytic activities. The SO42-/ZrO2 solid acid catalyzes mainly the hydro-cracking, ring-opening and hydrogenation reactions of coal to produce oil and gas during the coal liquefaction. The hydro-cracking reactions in the liquefaction of model compounds and coal catalyzed by SO42-/ZrO2 involved via carbenium ion intermediate instead of traditional radicals intermediate. (c) 2008 Elsevier Ltd. All rights reserved.