The self-developed portable surface plasmon resonance biosensor is used in the detection of highly toxic pesticide coumaphos, as the existing pesticide detection methods are complicated, with precious instrument, and not conductive to on-site rapid detection. The antibody direct detection experiments are conducted; the continuous detection method is proposed and preceded in small coumaphos molecules with concentrations of 500, 200, 100, 50 and 0 mg/L. The validity of this method and the device is demonstrated by experiments. The unmarked coumaphos detection method based on the surface plasmon resonance is simple. The developed device is portable and easy to operate. The rapid and real-time detection can be realized by this method.