Abstract Water-soluble feruloylated oligosaccharides (FOs) from wheat bran, ferulic acid esters of arabinoxylan oligosaccharides, have been reported as natural antioxidants. In this study, structure features of FOs were studied by FT-IR spectroscopy, and high-performance liquid chromatography (HPLC) coupled to electrospray ionisation (ESI) mass spectrometry (MS) was used for separation and characterisation of FOs. Four components of FOs were resolved on a Dikma Technologies Diamonsil™ C 18 column eluted with water/acetonitrite (90:10) containing 0.5% HCOOH (V/V) and further analysed by ESI-MS n . In ESI-MS n , a predominant [M+NH 4 ] + ion in positive mode and [M−H] − ion in negative mode were observed for molecular mass information. The ESI-MS n spectra of the deprotonated molecular [M−H] − ion were used for structural elucidation. The structures of four isolated compounds were confirmed for the first time by on-line HPLC-ESI-MS n .