Objective: To develop a reporter gene system based on transient transfections with a NF-?B responsive reporter gene to detect the bioactivity of IL-1? and IL-1 receptor antagonist.Methods: NF-?B reporter and Dual-Luciferase assays were applied to measure the bioactivity of IL-1? and IL-1 receptor antagonist in mouse EL4 cells(some subclones of EL4 cells expressed high level of IL-1 receptor on cell surface).pNF-?B-luc and pRL-TK, used as an internal control,were co-transfected into EL4 cells and then the IL-1? was added.Results: The results indicated that IL-1? was able to induce the expression of this luciferase,which could be blocked by IL-1 receptor antagonist. The optimal dose of IL-1? was 5(?g/L) in Dual-Luciferase assay,whose bioactivity can be effectively inhibited by IL-1ra at 50 ?g/L.Conclusion: We have established a new method to detect the bioactivity of IL-1? and IL-1 receptor antagonist,which can give repeatable results.