Voltammetric behavior of sodium 7-methoxyl-4’-hydroxylisoflavone-3’-sulfonate (SMHS) in the aqueous solu-tion from pH 1 to 5 was studied by linear sweep voltammetry, cyclic voltammetry and normal pulse voltammetry. Experimental results showed that in 0.2 molL-1 sodium citrate-hydrochloric acid buffer solution (pH=4.65), SMHS caused only one reduction wave at -1.34 V (vs. saturated calomel electrode, SCE), which was an irreversi-ble adsorptive wave of SMHS protonized involving one electron and one proton. The peak current of SMHS on lin-ear sweep voltammogram was proportional to its concentration in the range of 8.0×10-6—8.0×10-5 molL-1 (r=0.995), and the detection limit was 5.0×10-6 mol昄-1. The method was applied to determination of SMHS in syn-thetic samples. In addition, its scavenging effect on superoxide anion radical was studied by the auto-oxidation of pyrogallol in HCl-tris buffer solution (pH=8.2) in order to explain its peculiar biological effects. The experimental results proved that SMHS has antioxidant quality, and it is an efficient free radical scavenger of superoxide anion radical. Voltammetric behavior of sodium 7-methoxyl-4’-hydroxylisoflavone-3’-sulfonate (SMHS) in the aqueous solu tion from pH 1 to 5 was studied by linear sweep voltammetry, cyclic voltammetry and normal pulse voltammetry. Experimental results showed that in SMHS caused only one reduction wave at -1.34 V (vs. saturated calomel electrode, SCE), which was an irreversi-ble adsorptive wave of SMHS protonized involving one electron and one proton. The peak current of SMHS on lin-ear sweep voltammogram was proportional to its concentration in the range of 8.0 × 10 -6 -8.0 × 10 -5 mol L -1 (r = 0.995), and the detection limit was 5.0 × 10 -6 mol 昄 -1. The method was applied to determination of SMHS in syn-thetic samples. In addition, its scavenging effect on superoxide anion radical was studied by the auto-oxidation of pyrogallol in HCl-tris buffer solution ( pH = 8.2) in order to explain its peculiar biological effects. The experimental resu lts proved that SMHS has antioxidant quality, and it is an efficient free radical scavenger of superoxide anion radical.