Carboxylic acids are major components of bio-oil. Investigation of reaction characteristics of carboxylic acids during steam reforming contributes to understanding of the reaction behaviors of bio-oil in reforming process. Acetic acid is a major carboxylic acid in bio-oil. The research activities on acetic acid steam reforming have been intensified in recent years. A number of reforming catalysts, reforming processes and reactors have been developed. The catalysts developed differentiate from each other in terms of activity, stability and resistivity towards coking, due to their distinct elemental compositions, structural configurations and surface properties. The reforming processes and the reactors used for steam reforming of acetic acid also varies substantially, imposing profound effects on the reforming of acetic acid. To assess state of the art of the catalysts/process/ reactors develop for acetic acid steam reforming, a critical review is required to screen the intrinsic effects of these variables. This review focuses on the progress of steam reforming of acetic acid in three aspects: reforming processes, reactors and catalysts. The information from this review will be a useful reference for the research in steam reforming of bio-oil and other organics such as methanol, ethanol and acetone.