Objective To explore the treatment mechanism of safflower injection on sudden deafness through the changes of the hearing threshold, serum superoxide dismntase (SOD) and malonyldialdehyde (MDA) before and after treatment. Methods 40 cases of sudden deafness were divided into two groups: groupⅠ(group with safflower) and groupⅡ (group without safflower). The concentrations of serum MDA and SOD and hearing threshold were detected before and after treatment. 25 cases of normal hearing as the control group. Results (1) The total efficiency in the group Ⅰwas higher than the group Ⅱ (P<0.05). (2)The concentration of SOD was lower and the concentration of MDA was higher than that of the control group before treatment in both two groups (P<0.05). The concentration of SOD was higher and the concentration of MDA was lower after treatment in group I (P<0.05). The concentrations of SOD and the MDA had no significant change in groupⅡ (P>0.05). Conclusion Safflower injection could scavenge oxygen free radical and improve the quality of hearing recovery.