Vitamin D is a colorless crystal, soluble in fats, fat solvents and organic solvents, with stable chemical properties, heat-resistant in neutral and alkaline solutions, and not easily oxidized, but gradually decomposed in acidic solutions. The vitamin D aqueous solution is unstable due to dissolved oxygen, and its biological effect is significantly reduced after the reduction of the double bond. Therefore, vitamin D should generally be stored in a low temperature environment without light, acid, oxygen or nitrogen.