Objective： To solve the problem that determination results of two vitamin D₃ assay samples are unparallel by current national drug standards for calcium carbonate and vitamin D₃ preparations. To establish the accurate and reliable assay method about vitamin D₃. To support the quality control of calcium carbonate and vitamin D₃ preparations.Methods： Add 20 mL of 75% dimethyl sulfoxide to the powder of the preparation， and shake at 45 ℃ for 15 min， then take it cool. Add 15 mL of diluted solvent to 75% dimethyl sulfoxide layer， and stopper it， then shake it for 90 min. Centrifuge it at 3 000 r·min^-1 for 10 min， and withdraw the diluted solvent layer.Results： The average recovery of vitamin D₃ （n=9） was 99.12%， RSD （n=9） was 1.03%. 11 batches of calcium carbonate and vitamin D₃ preparations were determined. The standard deviation of the two parallel samples was less than1.1%.Conclusion： Vitamin D₃ is degrading by current national drug standards when ultrasonic extraction in 75% dimethyl sulfoxide. That brings the larger RSD of sample determination results. The method is accurate and reliable about shaking the samples of calcium carbonate and vitamin D₃ preparations. The suggestion is to amend the method in current standards as ‘add 20 mL of 75% dimethyl sulfoxide to the powder of the preparation， and shake at 45 ℃ for 15 min， then take it cool’.