The present invention relates to a process for purifying Doxercalciferol, a synthetic vitamin D analog, also known as 1α-hydroxy vitamin D2, to the purity greater than 99.5% by crystallization from a mixed solvent of methanol and acetonitrile. Each of the individual impurities can be controlled no more than 0.1% which meets the individual unknown impurities specification requirement of International Conference on Harmonisation (ICH) guideline. The crystallization yield is more than 75% which is suitable for employed as a commercial process.
