An innovative semi-dry flue gas purification technology with multi-spouted bed was proposed，and experimental study on desulfurization characteristics in the secondary reaction zone was performed by an on-line SO2 spectral measuring system.Five factors，including amount of desulfurating agent，flue gas temperature，particle concentration of circulation，strength of air flow disturbance，and amount of modulator water，which influence the quantity of removed pollutant and the removal ratio，were analyzed.The experiment indicates that with optimal parameters，the removal ratio of studied zone can reach more than 40%.It is found the particle concentration of circulation affects the desulfurization characteristics significantly，which can increase the removal ratio by 18%.The effect of amount of absorbent，strength of air flow disturbance and amount of modulator water on the removal ratio is increasing the removal ratio by 6%～8%.