Wet Biochemical Flue Gas Desulphurization technique (WB-FGD) is combined both catalyst of transition metal with microbial metabolize to achieve flue gas desulphurization. In the self-designed device of power plant flue gas desulphurization, study the desulphurization kinetics according to the absorption solution pH, Fe3+ concentration, inlet concentration of SO2, temperature and other factors. The results show that: Concentration of Fe3+ is the most critical factors in the desulphurization process, the desulphurization efficiency is decreased with the increasing of Fe3+ concentration, which in the range of 0~0.01mol·L-1, and the desulphurization efficiency do not change significantly with the further increasing of the concentration of Fe3+.the desulphurization efficiency is decreased with the increasing concentration of H+ when pH of the solution in the range of 1.5~3.5. The efficiency of desulphurization decrease with the increasing concentration of SO2, which in the range of 1145-3432mg·L-1. The oxidation rate increase with the increasing temperature at 20~40°C.The kinetic equation and controllable parameters of changes of Fe3+ concentration are obtained according to the experimental data in WB-FGD.