The invention provides a method for preparing special mirabilite with high purity, which comprises the following steps: pumping hot water at 40 DEG C-70 DEG C by a pump and dissolving mirabilite in ore to form niter water containing various impurities; calculating the content of added sodium carbonate with the excess of 10 percent-20 percent according to the detected content of calcium and magnesium ions in the original niter water during chemical impurity removal processing; calculating the content of added sodium sulfide with the excess of 20 percent-30 percent according to the detected content of heavy metal ions including ferrum, arsenic, lead, cadmium, antimony, and the like in the original niter water; then adding sodium hydroxide to lead the pH value of the niter water to reach 9-11; adding 0.1-0.3 percent by weight of polyferric sulfate and polyaluminum-ferric chloride sulfate to enable various generated sediments to settle; and finally adding sulfuric acid to adjust the pH value of the niter water to reach 7-7.5. The wet niter containing crystal water is processed by a fluidized bed after standing at 45 DEG C-80 DEG C for 0.5 hour-3 hours in a heat preservation way, thereby obtaining anhydrous special mirabilite with high purity. The mirabilite can not be caked during long-term placement at room temperature and can be widely applied to industries of foods, medicines, and the like.