NOVELTY - Preparing dehydroepiandrosterone, involves esterifying 10,13-dimethyl-1,6,7,8,9,10,11,12,13,14,15,16-dodecahydro-2H-cyclopenta(a)phenanthrene-3,17-dione (i), acetic anhydride and catalyst of para-toluenesulfonic acid to give 10,13-dimethyl-17-oxo-2,7,8,9,10,11,12,13,14,15,16,17-dodecahydro-1H-cyclopenta(a)phenanthren-3-yl acetate (ii); reacting compound (ii), glycol, water removal agent and catalyst of para-toluenesulfonic acid to give ketal product; reacting the ketal product and borohydride salt to form reduzate; and hydrolyzing the reduzate and acid to form dehydroepiandrosterone.    USE - For preparing dehydroepiandrosterone (claimed).    ADVANTAGE - The method provides dehydroepiandrosterone with high yield i.e. 80.79% after refining; and avoids the disadvantages of difficulty in controlling the production method, troublesome aftertreatment, and big risk and environment pollution in the traditional production method. The reaction condition of the method is easy to control. The after-treatment process is simple. The raw material used in the method can be prepared by processing microbial fermentation to sterol. The raw material has wide source, which is cheap and environment-friendly, and also can be purchased from human biological medicine.    DETAILED DESCRIPTION - Preparation of dehydroepiandrosterone, involves esterifying 10,13-dimethyl-1,6,7,8,9,10,11,12,13,14,15,16-dodecahydro-2H-cyclopenta(a)phenanthrene-3,17-dione (i), acetic anhydride and catalyst of para-toluenesulfonic acid to give 10,13-dimethyl-17-oxo-2,7,8,9,10,11,12,13,14,15,16,17-dodecahydro-1H-cyclopenta(a)phenanthren-3-yl acetate (ii); reacting the compound (ii), glycol, water removal agent and catalyst of para-toluenesulfonic acid to give ketal product of 10,13-dimethyl-1,2,7,8,9,10,11,12,13,14,15,16-dodecahydrospiro(cyclopenta(a)phenanthrene-17,2'-(1,3)dioxolane)-3-yl acetate, where the water removal agent is triethyl ortho-formate or trimethyl ortho-formate; carrying out reduction reaction between the ketal product and borohydride salt to obtain reduzate i.e. 10,13-dimethyl-1,2,3,4,7,8,9,10,11,12,13,14,15,16-tetradecahydrospiro(cyclopenta(a)phenanthrene-17,2'-(1,3)dioxolan)-3-ol (iii); and hydrolyzing the compound (iii) and acid to form the dehydroepiandrosterone.