The present invention discloses a sulfated derivative of polysaccharide extracted from gastrodia elata BL., the preparation method thereof and the use thereof in preparing antineoplastic medicaments, wherein, the gastrodia elata polysaccharide has the following structure: wherein, x and y are each an integer, and x+y=16, “n” is and integer, and the mean molecular weight of the polysaccharide from gastrodia elata is estimated as 2.8×105, the specific rotation of the polysaccharide is +95° in a 0.5 mg/mL aqueous solution thereof; the sulfated position is mainly at 6-hydroxy of the gastrodia elata polysaccharide, with mean molecular weight of 6.5×104 and a specific rotation of +150.0° in a 0.5 mg/mL aqueous solution thereof. In vivo and in vitro experiments indicate that the sulfated derivative of gastrodia elata polysaccharide can inhibit the tumor growth by suppressing the expression of Id1 to inhibit angiogenesis, and therefore has an obvious antitumor activity, and shows almost nontoxicity to endothelial cells, thereby having a good prospect of being developed into antineoplastic medicaments.