The invention discloses a preparation method for a pentosaccharide intermediate of anticoagulant drug fondaparinux sodium. Monosaccharide segments A, B, C and D are prepared through a novel synthesizing method, and the synthesizing steps are simplified; meanwhile, appropriate protecting groups are mainly selected to protect hydroxyl groups and carboxylic acid, the stereospecific glycosylation achievement in the later period is facilitated, and then the needed glycosidic bond types are obtained; in addition, the protecting groups can be removed in one pot, and therefore the synthesizing steps are shortened. The preparation route is practical, convenient to operate and feasible.