Abstract: AimTo separate and purify the anti-myocardial ischemic polysaccharide fraction with a homogenous molecular weight from Ophiopogon japonicus, then study the chemical structure of the parts. MethodsCrude polysaccharides were prepared by extracting the tube root fraction of Ophiopogon japonicus with water, then precipitation with ethanol. From the crude polysaccharides, the polysaccharide of MDG-1 was separated and purified using ultrafiltration, DEAE Sepharose FF and Sephadex G-25 column chromatography. Its structure was studied by complete hydrolysis, periodate oxidation, Smith degradation, methylation analysis, ¹H NMR and ¹³C NMR analysis etc. Results and ConclusionMDG-1 was a water-soluble β-D-fructosan, containing a backbone composed of Fruf (2→1), and a branch of Fruf (2→6)Fruf(2→ per average 2.8 of main chain residues. M_n, M_w and M_p of MDG-1 were 3 400, 4 800 and 5 000, respectively. MDG-1 contains trace of Glc, which maybe connect to its reducing terminal. Molar ratio of Fru and Glc is approximately 35∶1.