The change law of reaction dynamics was experimental studied through adding Vc to lotus root polyphenol-oxidase and dealing with lotus root polyphenol-oxidase (PPO) by magnetic field. The experimental results indicated that the reaction kinetic of enzymatic browning was accordant with Michaelis equation with catechol substrate, which Km and Vmax were 0.775 mol/L and 11.150U/min respectively. Vc had an inhibiting effect on lotus root PPO, which Km and Vmax were 0.081mol/L and 3.243U/min respectively. The browning was lagged and the lag time increased gradually with the rise in the concentration of the inhibitors, which was an anticompetitive inhibition. The PPO activity expressed a fluctuation at different magnetic field strengths and times. At 3.17A/m magnetic field strength for 4 hours, the reaction kinetics curve was a wave-type curve. The kinetic equations were established respectively.