Single-chain fragment variable(ScFv) antibodies with the substrate binding sites were obtained by repetitive selections from a semi-synthetic phage display antibody library against two haptens——thyroxine(T4) and O-methyl-T4(O-CH3-T4).The positive phage clones were determined by ELISA and then cloned into vector pET30a(+).The recombined plasmids were identified by DNA sequence analysis and transformed into E.coli BL21 (DE3).The expressed proteins were isolated,purified,identified by Western blot analysis,and finally the catalytic group——selenocysteine was incorporated into the antibodies binding sites by chemical mutation.The type Ⅰ thyroxine deiodinase activities of the abzymes were 0.006 and 0.008 pg·mL-1·min-1,respectively,which were about one tenth that of the mouse intact antibody that was obtained from hybridoma.