The objective of this research are (1) lignin isolating from black liquor of EFB pulp and its characterization involves purity; molecular weight distribution by GPC method; UV spectra, IR spectra, and percent of free phenolic hydroxyl and acetyl groups. (2) Acetylation of lignin isolated by acetate anhydride-pyridine respectively, then characterize derivated lignin involves UV spectra, IR spectra, and percent of free phenolic hydroxyl. The research showed that EFB lignin, that was isolated by 20% of sulfuric acid on pH = 1, temperature 60oC give 20.51% w/w, 87.30% purity, Mw = 2.752 x 105, Mn = 3.25 x 104, Mz = 3.208 x 105 and 8.47 of polydispersity index. UV and IR spectra of isolated lignin are very similar to standard lignin spectra. Base on the description above we cocluded that lignin successfully isolated from the black liquor of EFB organosolv process through precipitation method. Lignin derivatization also successfully carried out for giving acetylated lignin. The free phenolic group contents of lignin and acetylated lignin are 1.23 and 0.14% respectivel y. The main functional group of one molecule of EFB lignin that was isolated at pH = 1 and temperature 60oC are 199 of free phenolic hydroxyl groups, 1,765 of aliphatic hydroxyl groups. Keywords: Characterization Lignin, Empty Fruit Bunches, Acetylated Lignin, Organosolv Process