Abstract: Objective To explore the expression of platelets microparticles (PMPs) in peripheral blood (PB) and synovial fluid (SF) of rheumatoid arthritis (RA) patients and its correlation with clinical inflammatory parameters. Methods The levels of PMPs in PB were detected by flow cytometry in 26 active RA patients and 15 healthy control (HC). SF was collected from 16 patients. The percentages of CD62P⁺PMPs, CD154⁺PMPs and clinical parameters (including CRP, ESR, RF and ACPA) were also measured, then the correlations of PMPs with these parameters were analyzed. Results PMPs levels in PB of RA patients were higher than those in PB from HC and those in SF of RA patients (P< 0.01). CD62P⁺PMPs levels in PB of RA patients were higher than those in PB of HC and those in SF of RA patients (P< 0.05). CD154⁺PMPs levels in PB of RA patients were higher than those in PB of HC (P< 0.01) and those in SF of RA patients (P< 0.05). The levels of PB PMPs were positively correlated with disease activity score DAS28 ( r=0.462, P=0.018), but not with ESR, CRP, RF or ACPA. The levels of SF PMPs were not correlated with any of them (P>0.05). Conclusion PMPs may be involved in immune regulation and systemic inflammation of RA. The elevated levels of PMPs could be a potential biomarker for RA.