The product of HDX-A with a molecular weight over 6 000 ku was made from sodium alginate obtained by H₂O₂.And the mechanism of the HDXA enhancing the water-holding capacity of white leg shrimp was studied.The results showed that the weight of white leg shrimp significantly increased by 14.6 percent after being marinated in 1 percent solution for 1 hour.Also the drip loss and the cooking loss were lower than those of the control and phosphate compound treatments after being frozen 20 days.Although the ATPase activity of the HDX-A treatment reduced by 40 percent,it was lower than the untreated sample and the control.But there was no difference between the HDX-A treatment and the compound phosphate treatment in the ATPase activity.The physical characteristics of the HDX-A treatment sample were similar to the fresh sample except that the break strength became small.The result of the histology showed that the building and growth of the ice were affected by HDX-A during frozen storage.The holes were smaller and more in unit area than those of the control.The ratio of the hole whose area was less than 100 μm² was about 74.5 percent.The percentage of the other holes whose area were between 100-2 500 μm² was 25.5.There was no super big hole in the white leg shrimp muscle.