Abstract: Objective To study the changing rules of serum leptin levels in patients with rheumatoid arthritis（RA）. Methods Activity of RA was assayed according to the 28-joint count disease activity score（DAS28）.Serum levels of leptin,TNF-α,IL-1β,IL-6,RF,CRP,ESR and anti-CCP were measured in 40 healthy controls and 96 patients including 47 patients with active RA and 49 patients with non-active RA.Correlation between leptin and TNF-α,IL-1β,IL-6,RF,CRP,ESR and anti-CCP was analyzed. Results The serum levels of leptin,TNF-α,IL-1β,IL-6,RF,CRP,ESR and anti-CCP were significantly higher in patients with active RA than in healthy controls（P＜0.01） and the serum level of leptin was significantly higher in women than in men（P＜0.05）.No significant difference was observed in serum levels of leptin,TNF-α,IL-1β,IL-6,RF,CRP,ESR and anti-CCP between patients with nonactive RA and healthy controls.The serum level of leptin was significantly related with those of TNF-α,IL-1β,IL-6,RF,CRP,ESR and anti-CCP in patients with active RA（P＜0.05）. Conclusion Serum leptin level in RA patients is closely related the activity of RA,and leptin can act as a cofactor in promoting the progression of RA.