The invention discloses a comprehensive utilization method of an ammonium sulfate solution, which comprises the following steps: conversion, circulating absorption, mixing reaction and recovery. After the ammonium sulfate solution is added into a reaction tank for preparing phosphoric acid by decomposing phosphorite with strong acid, the sulfate is combined with calcium ions in the phosphoric acid slurry to generate insoluble calcium sulfate, and the ammonium ions reside in the phosphoric acid in the form of ammonium phosphate. By utilizing the characteristics of high solubility of the ammonium phosphate and high water content of the slurry in the phosphoric acid reaction tank, after the phosphogypsum is filtered, the ammonium phosphate enters the phosphoric acid, and the nitrogen element in the ammonium sulfate enters the subsequent system along with the phosphoric acid to prepare the compound fertilizer, thereby recovering the ammonium sulfate. The method effectively solves the problems of high ammonium sulfate treatment cost and high treatment difficulty.