The spectrophotometric determination of benzoyl peroxide(BPO) in wheat flour by KI-Acridine Red-PVA system was established.It was found that in the H2SO4 medium,BPO reacts with KI to give I-3,which further reacts with acridine red to form an ion-association complex and causing the absorbance of the solution decreased.Under 525nm,a good linear relationship was found between the absorbance and concentration of BPO and the average recovery was 98.2% and 101.6% respectively.Based on these facts,a simple sensitive and accurate spectrophotometric method for the determination of BPO was proposed.It has the advantages including easy operation,high sensitivity,good precision,and low consumption etc.,which can meet the requirements to detect benzoy peroxide residue in wheat flour samples.