In order to improve stability and uniformity of the fertilizer discharge in tropical orchards, the discrete element method based on EDEM was used to simulate the structural parameters of the fertilizer and carry out simulation experiments. The effects of screw blade diameter, pitch and the speed of exhaust shaft on the fertilizer discharge performance were analyzed to establish the regression mathematical model of the working parameters and the variation coefficient of the fertilizer discharge. The simulation results show that the factors affecting the fertilizer discharge rate of the spiral fertilizer are the rotation speed of the fertilizer discharge shaft, the pitch, and the diameter of the spiral blade in sequence. The maximum and minimum fertilizer discharge rate is 221.2 g/s and 54.76 g/s, respectively. The factors affecting the variation coefficient of fertilizer discharge stability is the speed of shaft, the pitch, and the diameter of screw blade. The optimal parameter combination is determined by Design-Expert 8.0 with the crew blade diameter of 100 mm, the pitch of 60 mm, and the rotation speed of 15 r/min. Under the optimal parameter, the variation coefficient of the fertilizer discharge stability reaches the minimum value of 8.48%. The fertilizer discharge performance of the fertilizer discharge is stable and uniform.