Abstract: The external groove wheel fertilizer applicator is an important carrier for the implementation of precision variable fertilization. In order to study the influence of the structural parameters of the external groove wheel on the fertilizer performance of the fertilizer applicator, this paper expounds the working principle of the external groove wheel fertilizer applicator, determines the main factors affecting the fertilizer performance of the fertilizer applicator, and constructs the mechanical model of the external groove wheel fertilizer applicator in the process of filling and discharging. Using discrete element software EDEM to simulate and analyze the fertilizer discharge performance of external groove wheel fertilizer discharger, the influence of groove wheel radius, arc center distance and groove number on fertilizer discharge performance is analyzed. The variation coefficient of fertilizer uniformity was selected as the evaluation index, and the radius of the groove wheel, the arc center distance and the number of grooves were used as the experimental factors. The single factor test of fertilizer discharge and the multi-factor test of fertilizer uniformity were carried out. The test results showed that there was a good linear relationship between fertilizer discharge and arc center distance, and the determination coefficient R2 was not less than 0.87. The primary and secondary factors affecting the fertilizer discharge performance are the groove wheel radius, the arc center distance and the number of grooves. The interaction between the groove wheel radius and the arc center distance has a significant indigenous effect on the fertilizer discharge uniformity. When the number of grooves is 6, the groove wheel radius is 27 mm and the arc center distance is 25mm, the optimal value of the fertilizer discharge uniformity coefficient is 91.12%. The bench test and the whole machine test of the outer groove wheel fertilizer discharger under the optimal structural parameters are carried out. The test results show that the fertilizer discharge uniformity coefficient of the fertilizer discharger is 91%～95%.