Objective To establish a method of preparation for biotinylated monoclonal antibodies.Methods Anti-IFN-α monoclonal antibodies were precipitated with saturated ammonium sulfate. We added 8μl of the BNHS reagent (38mg/ml) into 2.0 ml of the monoclonal antibody (6.0mg/ml),and incubated them at room temperature for 4 hours. Then add 48 μl 1M NH 4Cl into the mixture.10 minutes later,we applied the monoclonal antibody sample to the dialyses and got the purified biotinylated monoclonal antibody.The activity of the antibody was tested through the Avidin-biotin ELISA.Results The results showed that the antibodies kept high biological activities and sensitivities in detecting the sample of rhIFN-α. Conclusion The method is simple and stable.