Abstract: Trenbolone was chemically modified by succinic anhydride.Its hapten was synthesized and used to immunize animals,and specific monoclonal antibody against trenbolone was prepared.ELISA for detecting trenbolone was developed.Its sensitivity was 0.05 μg/L.Its cross-reactivity against trenbolone was 100%;that against boldenone and testosterone was less than 1%;and that against 19-nortestosterone was less than 4.5%.The recovery rate of beef samples added trenbolone at the concentrations of 2.5,5.0 and 10.0 ug/kg was 78.4%-105.6%.The coefficient of variation was less than 15%.This method is reliable to detect trenbolone residues.