The invention belongs to the field of medicinal chemistry, and in particular relates to a new crystal form A of docalciferol and a preparation method thereof. The invention also relates to a pharmaceutical composition containing the new crystal form A of docalciferol and its role in the treatment of osteoporosis Hyperparathyroidism or secondary hyperparathyroidism. The new crystal form A of docalciferol, using Cu-Kα radiation, X-ray powder diffraction at 2θ angles at 7.82, 8.51, 12.06, 13.01, 15.60, 17.05, 17.82, 18.71, 19.35, 20.06, There are diffraction peaks at 20.37, 20.62, 21.98, 22.68, 22.90, 23.81, and 24.79. At the same time, the invention also discloses a process improvement scheme for preparing high-purity doxercalciferol, which has simple steps, easy operation, short time consumption and low cost, and is very beneficial to large-scale industrial production.