Considering the problems of long detection time, poor reproducibility and limited resistance to light and temperature interference of equipment used for on-site detection of pesticide residues in the current market, a portable pesticide residue detector is designed based on enzyme inhibition and the data fusion algorithm. The system mainly includes an absorbance sensing module and a signal data fusion conditioning module. The absorbance sensing module uses front optical compensation path to eliminate common optical signal interference. The signal data fusion conditioning module groups and fuses the electrical signal in order to enhance signal authenticity. The test shows that the sensor system has good stability and reproducibility (relative standard deviation is lower than 2.5%), and the introduction of front optical compensation path eliminates the common optical signal interference effectively. Validation rate of samples whose inhibition rate is higher than 70% is up to 85%. When the sample inhibition rate reaches 50%, the pesticides in the concentration range of 0.5~5.0 mg/kg can be detected, which meets the demand of on-site detection.