Preparation method of delta 16 steroid

The invention relates to a preparation method of a delta 16 steroid. At the atmosphere of protective gas, a compound of a formula II, an oxidizing agent and sulfur dioxide are subjected to a reaction in an organic solvent, the reaction temperature ranges from minus 50 DEG C to 0 DEG C, and the reaction time is 1.5-2.5 h to obtain a delta 16 steroid I, wherein R1 is selected from H, halogen and acyloxy or hydroxide of C1-5; R2 is selected from alkyl of alpha C1-3 and alkyl or H of beta C1-2; R3 is selected from H, alkyl of alpha C1-3, alkyl of beta C1-2, alpha halogen or beta halogen; R4 and R5 are equal to H or double bonds; R7 is selected from H, and R6 is selected from H, alkyl of C1-3 or acyloxy of C1-5; or R6 and R7 are equal to double bonds. According to the preparation method of the delta 16 steroid, the 17-bit hydroxide compound of the formula II is used as raw materials, and the compound of the formula II is industrially produced and is easy to obtain; the preparation method is mild in reaction condition, no high-temperature strong base or strong acid is needed, fewer by-products are produced, the product yield and purity are high, the yield reaches more than 90%, and the purity reaches more than 93%.