AbstractIn this article, milled wood lignin (MWL) was isolated and purified from retted kenaf fiber, the lignin obtained was characterized by elemental analysis, FTIR, 1H‐NMR, and 13C‐NMR spectroscopy. The C9 formula is calculated for kenaf fiber MWL as C9H9.32O3.69(OCH3)1.30. The spectra of FTIR, 1H‐NMR, and 13C‐NMR show the kenaf fiber lignin to be of the G/S type with high proportion of syringyl (S) unit. The numbers of phenolic and aliphatic hydroxyl groups in the kenaf fiber MWL are estimated to be 0.14 and 1.31, respectively, per C9 unit. The OHaliph is 90.3% in total numbers of hydroxyl groups of kenaf fiber MWL, and the OHph is 9.7%. It is evident that the β‐O‐4 structures are mainly linkage in the MWL of kenaf fiber, which contain more erythro stereochemistry type in β‐O‐4 units than thero stereochemistry type. In general, the characteristics of lignin of kenaf fiber are similar to that of hardwood. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009