Mechanized fertilization has widely been one of the most important steps for the high yield of crops. In this study, a centrifugal side throwing fertilizer spreader was designed for the lotus root field. Firstly, atheoretical model was established for the force of a single fertilizer particle on the blade. The main parameters were then determined for the particle motion, such as the rotating speed of the fertilizer tray, the blade inclination angle, and the blade deflection angle. Secondly, EDEM discrete element simulation software was utilized to optimize the performance of the spreader. A single factor test was carried out, where the fertilizer feed rate and the above factors were taken as the influencing factors. The results showed that the fertilizer increased first and then decreased in a single statistical area when taking the center of the spreader as the origin along the throwing direction. Specifically, the quality of fertilizer with the most distribution in a single statistical region was called the peak value, and the distance between this region and the fertilizer spreader was called the peak distance, to accurately quantify the distribution index of fertilizer. The rotating speed of the fertilizer tray and the blade inclination angle posed a significant impact on the peak value and peak distance of fertilizer distribution, whereas, the blade deflection angle and feed rate on the peak value. An orthogonal rotation simulation test was carried out with the uniformity variation coefficient and peak distance as the evaluation indexes. It was found that there was an extremely significant influence on the uniformity variation coefficient (P<0.01), including the rotating speed of fertilizer tray, the blade inclination angle, the blade deflection angle, the interaction between them, the interaction term between the inclination angle of blade and feeding rate, as well as the quadratic term of blade inclination angle. There was an extremely significant effect on the peak distance (P<0.01), including the rotating speed of fertilizer tray, the blade inclination angle, and the quadratic term, the quadratic term of feeding rate. Design-Expert software was utilized to optimize the structure of the spreader. The blade structure parameters were then calculated to minimize the uniformity variation coefficient, when the peak distance was 10 and 21 m, the blade inclination, and deflection angle were 8.5° and 17.5°, 11.5° and -1.9°, respectively. Subsequently, the simulation and actual fertilizer application were carried out to evaluate the performance of the fertilizer spreader with the optimal structural parameters. The simulation results show that the uniformity variation coefficient, peak distance, and working width were 19.43%, 21 m, and 29 m, respectively, when the rotating speed of the fertilizer tray was 1 250 r/min, and the feeding rate was 0.316 kg/s. By contrast, the specific parameters in an actual contrast test were 21.95%, 18.6 m, and 24.5 m, respectively, where the errors with the simulation were 12.95%, 11.42%, and 15.51%, respectively. A performance test of fertilizer spreader was carried out with large particle urea, compound fertilizer, and phosphorus fertilizer commonly used in lotus root field topdressing. The results showed that the operation effect of large particle urea was better at 1 300 r/min, feeding rate of 0.15k g/s, and operation width of 24m. At this time, the uniformity variation coefficient was 24.56%. The analysis of variance showed that the rotating speed of fertilizer tray, feeding rate, fertilizer type, and the interaction term between fertilizer type and feeding rate presented an extremely significant impact on the coefficient of variation (P<0.01). The rotating speed of fertilizer tray, feeding rate, and type presented an extremely significant impact on the operation width (P<0.01). The finding can provide an important reference for the design of fertilizer spreading machinery in the lotus root field.