Objective: To investigate the relationship between platelets and serum thrombopoietin (TPO) in rheumatoid arthritis (RA) and the mechanism of RA with thrombocytosis thereof. Methods: The clinical data of 57 patients with RA were analyzed. Patients were divided into two groups by platelet count: high platelet count(>300×109/L) and normal platelet count. There were 28 healthy persons as control. Serum levels of TPO and interleukin (IL)-6 were measured using enzyme-linked immunosorbent assay(ELISA) in patients with RA and healthy controls. Results:(1)Serum TPO and IL-6 were higher in RA with thrombocytosis than those of healthy controls(P ＜ 0.05). Compared the two RA groups, the one with thrombocytosis had higher serum TPO(P ＜ 0.05). (2)The platelet count of RA with thrombocytosis did not correlate with serum level of TPO. It correlated significantly with serum level of IL-6 (r ＝ 0.566, P ＜ 0.01) and C-reactive protein (CRP) (r ＝ 0.401, P ＜ 0.05). (3)The serum level of TPO in RA with thrombocytosis did not correlate with serum IL-6 (r ＝ -0.069, P ＞ 0.05). Conclusion: The serum level of TPO was significantly elevated in RA with thrombocytosis, which suggested that TPO may take part in the pathology of thrombocytosis in RA. The thrombocytosis in RA correlated with inflammatory reaction.