Abstract: Water- soluble polysaccharides( ZMPs- W),extracted from floral axis of Zingiber mioga Rosc.by water extractingalcohol precipitation method were studied by the means of chemical and apparatus analysis.The antioxidation activities in vitro were also studied in this paper. The results showed that ZMPs- W were mainly constituted by galactose,glucose,galacturonic acid,glucuronic acid,arabinose,xylose,rhamnose( the mol ratio was 33.12 ∶ 18.79 ∶ 15.93 ∶ 11.47 ∶ 9.81 ∶ 5.98 ∶ 5.90). Triple helix structure,carboxyl group,sulfate group and pyran ring were found in the polysaccharides. The total sugar and protein content was 73.76% and 0.35%,respectively.Antioxidant experiment in vitro suggested that ZMPs- W had antioxidant activities.Under the experimental conditions,the antioxidant activities(·OH clearance,DPPH·clearance and Fe2 +chelation) increased with the increasing concentration.Especially,the clearance ablities of ·OH and DPPH· clearance were outstanding.