In this paper, the roles of Na2CO3 were investigated mainly for the lignite hydroliquefaction process with Fe-based catalyst. As a whole, Na2CO3 could play a synergistic role with Fe-based catalyst in obviously promoting the lignite conversion and the oil production and reducing water production. The synergistic effect mainly originated from these promotion actions of Na2CO3 to the depolymerization (for macromolecular structures in lignite) and hydrolyzation (for abundant oxygen-containing moieties in lignite). The promotion action of Na2CO3 for reducing water production was mainly attributed to the simultaneous promotion to the hydrolyzation of the ether bonds and carbonyl groups (especially ether bonds). The addition of Na2CO3 is more beneficial for the asphaltene conversion to oil than that for the preasphaltene conversion to oil in lignite hydroliquefaction with Fe-based catalyst. (C) 2015 Elsevier B.V. All rights reserved.