OBJECTIVETo develop a double antibody sandwich ELISA assay for quantitative determination of recombinant human interferon alpha1b.METHODSMouse monoclonal antibodies with different binding site on rIFN-alpha1b were screened to select optimized candidates as coating and HRP-labeled index antibodies respectively. And a double antibodies sandwich ELISA was assembled; the reliable lower detection limit, specificity, accuracy and reproducibility were evaluated and validated.RESULTSThe quantitative sandwich ELISA had a reliable lower detection limit of 10 ng/ml, with a liner detection range 10-100 ng/ml (R2 = 0.992), variation coefficient inter-plates is less than 10%.CONCLUSIONThe developed sandwich ELISA was a sensitive and specific, accuracy and reproducibility method for quantitative determination of recombinant human interferon alpha1b in final product.