Using flow cytometry(FCM) to measure IgG binding to red blood cells(RBC) exposed to H₂O₂ and their autofluorescence directly, in order to study the effect of H₂O₂ on the antigenicity and the production of fluorescent product of LPO of RBC. The results showed that the changes of both antigenicity and autofluorescence were dependent on the H₂O₂ concentration and the time of RBCs exposed to H₂O₂, and the change of antiginicity was more susceptible to H₂O₂ than that of autofluorescence. At 10² fold lower H₂O₂ concentration than that made autofluorescence significantly increase, IgG bond to RBC. Furthermore, it was found that the changes of antigenicity and autofluorescence were related to forward scatter (FSC).