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Aiming to address the issues of moisture absorption, low efficiency in topdressing operations, and poor uniformity in fertilizer distribution in the fertilizer top-dressing process for the large ridge double row planting mode of maize, a spiral conveyor fertilization device, multi row collection and airflow fertilization device suitable for this planting mode was designed based on the characteristics of fertilization operation. Theoretical calculations were conducted for the parameters of the spiral conveyor fertilizer discharging device and pneumatic conveying structure. The blade structure of the spiral conveyor was designed and the power of the spiral conveyor drive motor was determined according to the required fertilizer discharge rate. The structural dimensions of the main pneumatic fertilizer conveying pipeline and the pneumatic fertilizer distribution pipelines were determined. By merging the pneumatic fertilizer distribution pipelines using tee pipes, the fertilizer application rate in the middle of the double seedling rows was increased compared to the sides. Fertilizer discharging tests were conducted on this device, and the results showed that the spiral conveyor fertilizer discharging device provided stable fertilizer discharge, with the discharge rate linearly related to the rotational speed. A two-factor, three-level experiment was designed to investigate the effects of wind speed and fertilizer discharge rotational speed on fertilizer distribution uniformity. The rotational speed of fertilizer discharge, wind speed, and their interaction all had extremely significant effects on the coefficient of variation for uniformity in fertilizer discharge among rows. This coefficient was increased as both the rotational speed and wind speed increased. After merging the pneumatic fertilizer conveying pipes, the coefficient of variation for uniformity in fertilizer discharge among rows was slightly increased. The coefficient of variation for uniformity among rows without merged outlets ranged from 6.5% to 7.1%, while the coefficient with merged outlets ranged from 3.8% to 5.8%. The fertilizer discharge rate with merged outlets was approximately 1.7 times of that of the discharge rate without merged outlets. The fertilizer discharging performance met the design objectives and could effectively satisfy the mechanical operation standards for maize top-dressing.