Objective To establish a method for the measurement of soluble CD137(sCD137),measure sCD137 levels in the sera from patients with rheumatoid arthritis(RA) and estimate its significance. Methods Serum sCD137 and other immunological parameters,e.g.,CRP,RF in 30 patients with active RA,30 patients with inactive RA and 30 healthy controls were measured by streptavidin ELISA(SA ELISA) established and immunological rate nephelometry respectively.Results SA ELISA had good linearity,sensitivity,specificity,reproducibility and accuracy.The positive percentage and level of serum sCD137 in active RA group were significantly higer than that in inactive RA group and control group( P <0 01).There was significantly positive correlations between sCD137 levels and CRP,RF in active RA group( P <0 01). Conclusion sCD137 can be reliably measured by SA ELISA,sCD137 might be a valuable parameter for reflecting the activity of RA.