A kind of portable device for measuring concentration of pesticides used with enzyme sensor was designed. It included screen-printed enzyme electrode, signal conditioning circuit and MCU C8051F040. The preparation of enzyme electrode made the coated resistance of charge transfer reduced, charge transfer accelerated; and a reliable liner relationship between the inhibition of enzyme and log ［carbaryl］ was obtained from 5ng/mL to 2μg/mL, with the detection limitation of 1.7ng/mL. Response time of the device was less than 161s. The size of the device was small and the power was supported by battery. It provided a portable device for rapid measuring and spotty concentration of pesticide in μg/L level.