〔Abstract〕 Objective To explore the effect of the addition of N-acetylcysteine(NAC) on the abnormal increase of reactive oxygen species(ROS) during platelet cold storage, and to clarify its function of preventing the platelets from being recognized and cleared by macrophages and hepatocytes. Methods Platelets Concentrates were divided into room temperature group(22C), cold storage group(4C) and NAC addition group. In NAC addition group, the platelets were supplemented with 5 mmol/L(N5) and 25 mmol/L(N25) NAC. After 5-day storage, the levels of ROS, activation markers and other index of platelets in each group were detected by flow cytometry. Platelet phagocytosis was detected by PMA-activated THP-1 cells or by primary cultured HepG2 cells. Results After 5 days of storage, ROS increased significantly in 4C group than those in 22C group(P<0.05), and after NAC addition, ROS level reduced significantly(P<0.05). The expression of CD62P and PS and the exposure of β-GlcNAc on platelets in N5 group significantly decreased compared with those in 4C group(P<0.05). The platelet phagocytosis by THP-1 and HepG2 cells were also significantly lower in N5 group than those in 4C group(P<0.05). However, the addition of 5 mmol/L NAC did not significantly affect the count, pH, CD42b expression, β-Gal exposure and coagulation function of cold-stored platelet after 5-day storage. Conclusion The addition of NAC to refrigerated platelets can significantly decrease the level of platelet ROS and effectively reduce their phagocytosis by cells, suggesting that NAC addition may protect refrigerated platelets from being cleared by phagocytosis after transfusion.