Obejective To assess the influence of apheresis and wash on platelet function and morphology.Methods To determine the count,size,distribution,agglutination,aggregation,GMP 140 & GPⅡb/Ⅲa of the platelet from the peripheral blood prior to apheresis and aphersed or washed platelets produced by CS 3000 plus.Results Both apheresed and washed platelets showed decreased PDW,PCT & MPV,but there were no statistical difference between groups.There were no difference in platelet adhesion,aggregation,CD 62p +,CD 41a +,and CD 62p +expression.Both apheresed and washed platelets showed increased CD 41a + expression,but there was no difference between apheresed and washed platelets.Conclusion Flow cytometry measurement of GMP 140 & GPⅡb/Ⅲa may be used for in vitro platelet function assessment.Although apherisis can induce mild platelet activation,platelets apheresed or washed by CS 3000 plus have reliable quality and can be used in a variety of clinical conditions.