The invention relates to a method for refining sodium sulfate powder from chromium-containing mirabilite. The method comprises the following steps: a) grinding the chromium-containing mirabilite in the presence of water to prepare water-containing slurry; b) regulating the pH of the water-containing slurry obtained in the step a) with sulfuric acid to 2-3, and then adding sodium sulfite to reduce hexavalent chromium in the water-containing slurry to trivalent chromium, thus obtaining a saturated or over-saturated sodium sulfate water solution; c) stirring and crystallizing the saturated or over-saturated water solution which is obtained after reduction in the step b); d) filtering out crystals obtained in the step c); e) washing the crystals obtained in the step d) with the saturated sodium sulfate water solution; f) re-crystallizing the washed crystals obtained in the step e) with a saturated neutral sodium sulfate water solution to obtain the sodium sulfate powder. According to the method provided by the invention, additional heating is not required, the energy consumption is low, the obtained sodium sulfate powder has high yield and high purity, the content of sodium sulfate can achieve 99.00-99.90wt%, and the chromium content does not exceed 5ppm.