In view of the complex environment of paddy field, the end of the discharge port of the existing fertilizer application machinery is easily blocked by soil, resulting in the poor discharge performance of the fertilizer application machine, this paper designs a two-stage fertilizer discharge device, which can then reduce the blockage phenomenon at the end of the discharge port while improving the uniformity and continuity of fertilizer discharge. Firstly, the overall structure of the rice fertilizer application device is designed. The kinematic and kinetic analyses of key components were then carried out, and the results showed that the double gear pitch and gear speed had an important influence on the fertilizer discharge performance of the double-gear fertilizer discharger; the diameter, speed and pitch of the screw shaft had an important influence on the fertilizer discharge performance of the screw fertilizer discharger. The test results show that the uniformity of fertilizer discharge decreases and then increases with the spacing between the two gears, and when the spacing is 5mm, the fertilizer discharge performance of the double-gear fertilizer discharger is better; the coefficient of variation of fertilizer discharge stability increases with the gradual increase of pitch and diameter, and decreases and then increases with the gradual increase of rotational speed, and the combination of spiral shaft diameter, pitch and rotational speed is selected for the test. The best combination of spiral shaft diameter, pitch and rotational speed was determined as 21.292 mm, 134.07 r/min and 16.437 mm pitch, and the coefficient of variation of fertilizer discharge stability was 2.5%. The key components were designed according to the simulation parameters, and the transmission ratio of the double-gear fertilizer discharger and the spiral fertilizer discharger was determined to be 1:4 by combining theoretical calculations and discrete element simulation tests, which resulted in continuous and uniform fertilizer discharge. Finally, a comparison test between the two-stage fertilizer discharger and the spiral fertilizer discharger was conducted, and the test results showed that the consistency, stability and uniformity coefficient of variation of the two-stage fertilizer discharger were improved compared with the spiral fertilizer discharger.