A new pesticide residues detection instrument based on enzyme inhibition method is developed. The amount of pesticide residues is determined by measuring the light absorbency of the sample liquid after inhibition reaction. The influence of temperature on the activity of enzyme and the inhibition rate of enzyme is analyzed. A new method of temperature calibration based on RBFNN (Radial Basis Function Neural Network) is applied in the system, so that the instrument can accomplish precise measurements without the thermostatic device and overcome the shortcomings of these kinds of instruments. Experimental results show that the instrument of using RBFNN compensation have detection accuracy, high sensitivity, small size and low power consumption characteristics.