Abstract: A piezoelectric immunosensor coupled with a flow injection system was developed for detection of pesticide residues in the sample. Three methods for immobilization of the anti-organophosphorus pesticides monoclonal antibody onto the surface of a gold electrode on quartz crystal were compared for effective capture of organophosphorus pesticides. In the range of 0.005～10 μg/mL, there is a good correlative relationship between the concentration of organophosphorus pesticides and the frequency shift, and the regression equation is y = 5.9111Ln(x) + 51.979 with R2 = 0.93. The detection limit is 2.16×10-3 μg/mL. The immunosensor could be used repeatedly with good selectivity.