Magnesium reduction method for phosphorite

The invention discloses a magnesium reduction method for phosphorite, comprising the following steps: uniformly mixing the phosphorite with P2O5 grade of 28 percent to 30 percent and MgO grade of 1.8 percent to 3.5 percent with water, magnesium bisulfate, sulfuric acid, phosphoric acid and sodium aliphatate to react, wherein hydrogen phosphate radical ions replace carbonate radical ions in dolomite, magnesium ions are combined with fatty acid radical ions in the sodium aliphatate and form foams with carbon dioxide gas, and the dolomite overflows by adhering in the foams to finish magnesium reduction of the phosphorite. The method has low ore dressing cost, solves the problem that high magnesium phosphate concentrate ores produced by the prior positive flotation technology can not be used for producing high-quality diammonium phosphate, and particularly lowers the weight percentage content of MgO in the phosphorite (collophanite) of a medium or low grade to below 1 percent.