Abstract: The free phenolic acids(FPA),soluble covalent phenolic acids(HPA) and bound phenolic acids(BPA) were extracted and analyzed by high performance liquid chromatography(HPLC),and the antioxidant activities of phenolic acids(PAs),which including 1,1-diphenyl-2-picrylhydrazyl(DPPH) radical scavenging capacity,ferric reducing power and hydroxyl radical inhibiting capacity were determined. The results showed that the contents of PAs showed the following tendency:Red pulp > white pulp > white peel > red peel. The HPA was the main PAs in pulp and the BPA was the main PAs in peel of pitaya. Gallic acid(1700.70 μg/g DW) was the dominated PAs in red pitaya,and protocatechuic acid(1877.50 μg/g DW) was the dominated PAs in white pitaya. The BPA of red peel possessed the highest DPPH radical scavenging capacity(2206.37 mg/L),HPA of white pulp had the strongest reducing ability(A₇₀₀=0.82) and HPA of white peel owned the uppermost hydroxyl radical inhibiting capacity(77.50 U/mL). The correlation analysis of contents and antioxidant activities showed that DPPH scavenging ability and ferric reducing power were significantly(P<0.01) correlated with PAs contents,while hydroxyl radical inhibiting capacity was independent of the PAs contents.