Oligosaccharides were obtained from agar by enzymatic hydrolysis. Activated carbon adsorption separation was used to extract oligosaccharides, and gel chromatography separation was applied to further purify oligosaccharides. The result showed that activated carbon adsorption could remove the most salt impurities, and gel column chromatography could give the separation of the two kinds of oligosaccharides. ESI-MS, (13)C-NMR revealed that the molecular weight (Mw) of two oligosaccharides were 630 and 936, which were identified as neoagarotetraose and neoagarohexaose respectively.