Abstract: An ELISA method was established to detect the autoantibodies to GPⅡb/ Ⅲa in ITP plasma. In the plasma from 20 ITP patients, 5 gave positive result,indicating the presence of anti-GPⅡb/ Ⅲa autoantibodies. This result, suggested that in plasma from some ITP patients （25%）, there were autoantibodies to GPⅢb/Ⅱa which might recognise different antigenic sites of GPⅢb/Ⅲa. At the same time. the platelet number and platelet volume were measured by Hematology Series 810 Platelet Analyser from, 12 ITP patients for 80 person-time. It was found that there is aninverse relation-ship between platelet number and volume, r=-0.96, p value 0.01. It suggested that platelet size did not correlate with platelet age in ITP.