A one step method was employed to synthesize D-biotin I from dibenzyl biotin Ⅱ in order to solve the problems of high energy consumption, pollution and toxicity caused by the two-step reaction of debenzyl hydrobromate and ring closure. Optimal reaction conditions were identified via optimization solid Lewis acid type and solvent type, molar ratio of Lewis acid to dibenzyl biotin Ⅱ, reaction temperature and reaction time, followed by product structural characterization by FTIR, NMR, HPLC and LC-MS. The results showed that the product yield was higher than 90% and HPLC purity reached 99% when using aluminum chloride, aluminum bromide, zinc chloride and zinc bromide as Lewis acid, trifluoromethyl as solvent, and n(Lewis acid):n(dibenzyl biotin Ⅱ) kept at 2:1, reaction temperature at 70~75 ℃ and reaction time for 2 h.