A series of oligomannuronates with series degree of polymerization（DP28） were prepared by acid hydrolysis from alginate-derived homopolymannuronate blocks, and the structures of the oligosaccharides were analyzed. The macromolecule of alginate was treated by partial acid hydrolysis and fractionated at pH2.85 resulting in homopolymannuronate blocks. The homopolymer was degraded by acid hydrolysis, and the oligosaccharides were separated and purified by gel chromatography. The oligosaccharides were characterized by fluorophore-assisted carbohydrate electrophoresis（FACE）, and the structures of derived oligomannuronates were determined by ESI-MS, NMR as well as FTIR analysis.
