Abstract Aiming at the problems of low utilization rate of corn fertilizer, low precision of fertilization ratio, and time-consuming and laborious topdressing in the later stage, an U-shaped fertilization device with uniform fertilizer mechanism was designed. The device was mainly composed of uniform fertilizer mixing mechanism, fertilizer guide plate and fertilization plate. Compound fertilizer was applied on both sides and slow/controlled release fertilizer was applied at the bottom to form an U-shaped distribution of fertilizer around corn seeds. Through theoretical analysis and calculation, the structural parameters of the fertilization device were determined. Through the simulated soil tank test, the quadratic regression orthogonal rotation combination design was carried out on the main factors affecting the spatial stratification effect of fertilizer. The optimal parameters were obtained as follows: the stirring speed of the stirring structure was 300 r/min, the bending angle of the fertilization tube was 165°, and the operating speed of the fertilization device was 3 km/h. The results of bench verification test showed that under the optimized stirring speed and bending angle, the fertilizer particles were stirred evenly, and the average values of fertilizer flowing out of the fertilization tubes on both sides were 299.5 g and 297.4 g, respectively. The average fertilizer amounts of the three fertilizer outlets were 200.4 g, 203.2 g and 197.7 g, respectively, which met the agronomic requirements of 1:1:1 fertilization, and the variation coefficients of fertilizer amounts on both sides of the fertilizer pipe and each layer were less than 0.1% and 0.4%, respectively. The simulation results of the optimized U-shaped fertilization device can achieve the expected U-shaped fertilization effect around corn seeds. The results of field experiment showed that the U-shaped fertilization device could realize the U-shaped proportional application of fertilizer in soil. The distance between the upper end of fertilization on both sides and the distance between the base fertilizer and the surface were 87.3–95.2 mm and 197.8–206.0 mm, respectively. The transverse distance between the fertilizers on both sides was 84.3–99.4 mm, and the error with the designed theoretical fertilization was within 10 mm. Compared with the traditional side fertilization method, the number of corn roots increased by 5–6, the root length increased by 30–40 mm, and the yield increased by 9.9–14.8%.