NOVELTY - Preparing ginsenoside Rd by utilizing microbial conversion comprises: (a) setting Aspergillus niger strain (deposited under CICC40426) in the fermentation culture medium for culturing; (b) adding glycol type ginsenoside in full automatic fermentation tank for fermenting and converting; (c) adding macro-porous resin with full-automatic fermentation tank, gathering product; (d) using HP20SS macro-porous resin column chromatography purification to obtain the ginsenoside Rd; and (e) preparing crystal prepared by step (d) of ginsenoside Rd to purify, to obtain high purity ginsenoside Rd.    USE - The method is useful for preparing ginsenoside Rd by utilizing microbial conversion (claimed).    ADVANTAGE - In the method, a high-conversion industrial Aspergillus niger strain with culture preservation number being CICC40426 is adopted, various glycol-type ginsenosides are obtained by fermentation and conversion in a full-automatic fermentation tank, and high-purity ginsenoside Rd is prepared through purification and crystallization by virtue of macroporous resin. The method is simple in process, low in cost and high in yield and is environment-friendly; and with adoption of the method, industrial preparation of the ginsenoside Rd can be realized, source of the ginsenoside Rd drug resource is expanded, and wide medical care market demand is met, so that the method has great value.    DETAILED DESCRIPTION - Preparing ginsenoside Rd by utilizing microbial conversion, where Aspergillus niger strain is used in the full-automatic fermentation tank, fermenting and converting each kind of diol type, passing through macroporous resin purification and crystallizing for preparing high purity ginsenoside Rd, specifically comprises: (a) setting Aspergillus niger strain (deposited under CICC40426) in the fermentation culture medium for culturing; (b) adding glycol type ginsenoside in full automatic fermentation tank for fermenting and converting; (c) adding macro-porous resin with full-automatic fermentation tank, gathering product; (d) using HP20SS macro-porous resin column chromatography purification to obtain the ginsenoside Rd; and (e) preparing crystal prepared by step (d) of ginsenoside Rd to purify, to obtain high purity ginsenoside Rd.