Abstract: To measure polysaccharide contents in different parts of pitaya flower with white flesh and explore the differences in antioxidant activity in vitro.Extract polysacchardies from different parts of pitaya flower with white flesh by hot water extraction,and measure antioxidant capacity in different parts of polysacchardies by total antioxidant capacity and hydroxyl radical test boxes.The results showed that there′s an extremely distinct difference for polysaccharide contents in different parts,and the highest content was in the style which reach(148.67±7.13)mg·g^-1.The polysaccharides in different parts of pitaya flower possessed potent antioxidant activity,showing a positive concentration effect relationship for total antioxidant capacity,and scavenging hydroxyl radical.The ability to total antioxidant capacity order was style>calyx>petal>pistil.The ability to scavenging hydroxyl radical order was calyx>pistil>petal>style.