Background: Platelet microparticles (MPs) are produced automatically during platelet Storage. Their size is about 0. 1 – 1 μ m and have ability for sub-endothelium adhering, strengthen of platelet aggregation and also platelet pre-coagulation. In fact, the release of membrane particles helps to signal to the neighbor cells or to seclude target cells from apoptosis. The purpose of this study is to determine the effect of time passing on platelet MPs production. Methods: In this experimental study, 12 units of PC from healthy donors were obtained. Sampling was done at 2, 3, 5 and 7 days after Storage. After separating of MPs, they were prepared for flow cytometery analyses by anti-CD41a FITC and assessed their concentration through Bradford methods. Paired sample T-test and ANOVA were used to compare the results and investigatethe probable significant differences of this experiment. Results: There was no significant difference in platelet MPs concentration between PC stored in day 2 and 3. (P> 0. 05) On the other hand, we could claim significant differences in platelet MPs concentration between PC stored in day 3 and day 5 and also between day 5 and day 7. (P< 0. 05) Conclusions: We showed that the production or releasing of platelet MPs were considerable by passing time. Alsoby increasing of Storage time, platelet component included more MPs which were able to signal and produce interaction with other cells in patient receiving bodies. As a result, it was possible to interfere in their immune responses, inflammatory or coagulation processes after transfusion.