The invention relates to a production process of a high tower melt-granulated compound fertilizer. Potassium chloride is added in the process of melting urea, and the temperatures of urine and slurry are reduced according to a characteristic that the melting temperature is reduced after the urea is mixed with the potassium chloride serving as a cosolvent. The liquid solid ratio of the slurry can be regulated so as to reduce the melting temperature of the urea, the melting capacity of urea melting equipment is improved, and the foundation for improving the yield is laid.