In this study, a new systematic method for quantitative diameter analysis of sprayed pesticide droplets was developed. This method adopts the screw motion with precision motor and uses the vibration frequency of the precision control technology. With this method, the bubbles contained in the pesticide droplets were eliminated and the generated droplets are no longer adhere to the tip. The accuracy of this method is significantly improved compared with the previously manually operated device. The results indicated that with the calibration coefficient, the error between of the actual droplet size and the preset droplet size value was 97.2 %. This newly developed method is very valuable for future studies of droplet distribution over crop leaves for reducing the amount of pesticides sprayed on the crops.