To address the problem of poor fertilization uniformity in the spiral inclined fertilization device during operation, optimization and verification of the structural and motion parameters of the spiral components were carried out on the Longzhou 2FH series fertilizer-discharging device. By analyzing the fertilizer-filling and discharging processes of the device, the influence of its structural and operating parameters on fertilization uniformity was explored. Based on the requirements of fertilizer-discharging amount, the parameter ranges of the fertilizer-discharging components were determined. Single-factor tests were carried out with the average fertilizer-discharging amount and the coefficient of variation of fertilization uniformity as the operation quality evaluation indicators, and the parameter ranges of the inclination angle of the Y-shaped fertilizer-discharging pipe, the pitch of the conveying screw, and the rotational speed of the conveying screw were determined. An L9(33) orthogonal array was used to design the test. According to range analysis and variance analysis, the optimal combined parameters, the inclination angle of the Y-shaped fertilizer-discharging pipe 40°, the pitch of the conveying screw 36 mm, and the rotational speed of the conveying screw 170 r/min were obtained. In the bench-test, with the traveling speed of the device at 0.25 m/s, the average fertilizer-discharging amount and the coefficient of variation of fertilization uniformity were 3.48 g and 14.9%, respectively. Compared with the device before optimization, the average fertilizer-discharging amount increased by 0.78 g, and the coefficient of variation of fertilization uniformity decreased by 9.1 percentage points.