【Abstract】ObjectiveTo introduce a new approach for site-specific conjugation of Fab’ fragments of mouse monoclonal antibody (MoAb) to a bifunctional chelator 6-〔p-(bromoacetamido)benzyl〕-1,4,8,11 -tetraazacyclo-tetradecane-N,N′,N″,N-tetraacetic acid (BAT).MethodsFab’ fragments of B43 MoAb were obtained by a simple twostep method： 1, stable F(ab’)2 was produced by pepsin treatment of B43 MoAb. 2, Fab’ was obtained by reduction of the F(ab’)2 with cysteine. Fab’ fragments were directly conjugated with BAT. ResultsFab’ contained about 1.8 free thiol per molecule. The conjugation rate was 74% and each Fab’ fragment carried 1.28 BAT. The F(ab’)2, Fab’ and Fab’-BAT all maintained good biologic activity. ConclusionThis study may provide a simple and efficient method conjugating of MoAb Fab’ fragments to BAT.