The invention provides a phosphorite decomposition method which comprises the following steps: S1, leaching out phosphorite by using a mixed solution of phosphoric acid and a solutizer so as to obtain a lixivium and leaching residues; and S2, extracting the lixivium by using sulfuric acid, thereby obtaining ardealite and a phosphoric acid solution. As the phosphorite is decomposed by using the mixed solution of the phosphoric acid and the solutizer, not only are the decomposition ate of phosphorite and the recycling rate of phosphorus increased, but also the amount of the mixed solution for leaching out the phosphorite is reduced, that is, the phosphorus recycling rate is increased on premise that a liquid-solid ratio is reduced. Correspondingly, the amount of the mixed solution is reduced, the liquid-solid ratio of gypsum to extraction residue pulp after the extraction step is reduced, furthermore the treatment amount of the pulp is reduced, and the production efficiency is improved.