Synthesis of tributyl citrate (TBC) has been studied by using acid functionalized ionic liquid as catalyst. The results indicated that acidic ionic liquids show good catalytic and reusable performance. Under the optimum conditions, using 1-methyl-3-(3-sulfopropyl)-imidazolium hydrogen sulfate as catalyst, the conversion of citric acid was 97%. After easily separated from the products the ionic liquid could be reused 13 times without any disposal, and the conversion of citric acid was not less than 93%. Therefore, an environmental friendly approach for the synthesis of tributyl citrate is provided. Crown Copyright (C) 2009 Published by Elsevier B.V. on behalf of The Institution of Chemical Engineers. All rights reserved.