Objective To set up a method of detecting platelet associated antibody(PA Ig) by flow cytometry(FCM),and to investigate the value of FCM method in the diagnosis of idiopathic thrombocytopenic purpura(ITP).Methods We detected the platelet associated antibody of 20 healthy donors and 10 patients with ITP.These samples were also measured with ELISA.The results of FCM were compared with the results of ELISA.Results By FCM,the measured value of PA IgG,PA IgA and PA IgM,from 20 normal dornors,were 2.56?2.08%、13.75?5.98% and 13.90?7.28%,respectively.In patients with ITP,PA IgG,PA IgA and PA IgM were 28.13?17.74%、25.07?16.84% and 23.22?17.85%.Conclusion FCM can be a rapid,sensitive and new method in detecting platelet autoantibody,and has better potential than ELISA.