Abstract: Objective To investigate the effects of insulin on the expression of whole-blood platelet membrane P-slectin. Methods Flow cytometry (FCM) was used to detect the expression of whole-blood platelet membrane P-slectin, and the effect of insulin on the expression on quiescent and activated plasma platelet observed in normal young subjects. Results Insulin had no effect on the P-slectin expression on quiescent platelet membrane, but significantly inhibited the up-regulation of P-slectin expression induced by thrombin and collagen respectively, exhibiting dose- and time-dependent effects. Conclusion Insulin can inhibit P-slectin expression on activated platelet membrane.