Abstract: The kinetics of L-ascorbic acid (H_2A) oxidation catalysed by Cu(Ⅱ) -Tyrosine complex has been studied in phosphate buffer (pH=7.44) at room temperature. The rate of Cu(Ⅱ)-Tyr_2 catalysed reaction comformed to the Michalies-Menten equation with respect to ascorbate (K_m=4.29×10~(-4) mol L~(-1); v_(max)=1.66×10~(-4) mol min~(-1)). H_2O_2 and O_2~- were produced during this reaction. The rates were decreased due to add the CAT or SOD respectively, A mechanism has been proposed.