Lentinan， Laminarin and Lycium barbarum polysaccharide（LBP） were extracted by ethanol subsiding method and deproteinized by Sevage method. EDTA-2Na was used to remove the metal ions from crude polysaccharide and deproteinized polysaccharide. The antioxidant activity and antitumor activity of the polysaccharides were investigated by various assays， and compared with those of metal ions loss. The results showed that three fractions contain various intrinsic metal ions including Al， Ca， Mn with different amount. The ABTS radical scavenging， DPPH radical scavenging ability decreased after the metal ions removal. The change of hydroxyl radical scavenging ability was inconsistent among the investigated polysaccharides. Among them the activity of LBP decreased most significantly at 600 μg/mL， the scavenging activity of LBP on the ABTS radical decreased from 26.31% to 17.25% and the DPPH radical decreased from 59.80% to 38.40%. The antitumor activity against MCF-7 human breast cancer cells also decreased after the deproteinized LBP was treated by EDTA-2Na. We hence proposed that the intrinsic metal ions are a part of the active center in polysaccharides， which has an important effect on its activities.