① The viscosity of the material in the formula is the basis of granulation. When low concentration fertilizer is produced by using superphosphate as the phosphorus source, the conditioning agent of superphosphate and viscous material should be greater than 50%. When high-concentration compound fertilizer is produced by using ammonium phosphate as the phosphorus source, the conditioning agent of ammonium phosphate and viscous material should not be less than 40%. Urea formula depends on the amount of urea. The proportion of viscous materials in high-viscosity urea is generally about 35%. ② The ingredients used in the formula must be conducive to improving the roundness of the particles. The decomposition and softening temperature of dispersive materials (potassium chloride, ammonium chloride, potassium sulfate, ammonium sulfate, etc.) is relatively high, which can increase the strength of the particles in the dryer and play a key role in improving the roundness of the particles. The sum of dispersible materials in the formula should account for more than 35%.