A closed loop control system for adjusting fertilizer scatters breath was developed based on the PWM technology. The module circuit, sensor installation and close-loop feedback method were designed. The relation of disc rotation speed and scatters breath was built with experiment. The breadth value could be input to system directly according to the operation needs, so the rotating disk could work under specifying speed which improved operated performance and intelligence of the machine. Experiment showed that with the different operation speed and different width scatters, the maximum error and the minimum error between actual scatters breadth and target scatters breadth was 5.50% and 2.86%, respectively. The designed system can meet the practical production requirements.