The invention provides a method for preparing 3 beta, 7 beta-dihydroxy-15 beta, 16 beta-methylene-5-androstene-17-ketone by a microbial transformation method. The method uses Botryodiplodia malorum CBS13450 as a strain and comprises the steps of preparing a resting cell transformation system and transforming a substrate, wherein the resting cell transformation system comprises a buffer solution which is selected from a phosphate buffer solution, an acetate buffer solution, a phosphate-citric acid buffer solution, a monopotassium phosphate-sodium hydroxide buffer solution or a citric acid-sodium hydroxide-hydrochloric acid buffer solution. Under the optimal transformation conditions, the system has a transformation result that 0.3 percent of substrate is fully transformed within 45 hours.