The invention discloses a O, O-dimethyl-O-[-3-methyl-4-amino phenyl] thionic phosphate (FNH2) as fenitrothion hapten, artificial antigen and specific antibody, which is characterized by the following: reducing nitro in the fenitrothion molecular structure into amino under acid condition with zinc powder; reacting to obtain the hapten molecule in connection with carrier protein; diazotizing to couple hapten and protein to obtain immunogen and peridium; using immune animal with immunogen to make the specific antibody.