The invention provides a microbial cell conversion method for producing 2-keto-D-gluconic acid. The method comprises the steps of A. preparing resting cells with a genetic engineering strain of gluconobater oxydans DSM2003 as a strain, wherein the genetic engineering strain is gluconobater oxydans of overexpressing gluconic acid dehydrogenase, and the gene of the gluconic acid dehydrogenase comes from the gluconobater oxydans and has a nucleotide sequence as shown by SEQ ID NO:1; B. preparing a conversion liquid containing glucose or gluconic acid, wherein the concentration of the glucose is 200-250g / L, and the concentration of the gluconic acid is 200-300g / L; and C. adding 30-60g / L of resting cells into the conversion liquid for converting so as to obtain the 2-keto-D-gluconic acid. The method has the advantages that the conversion rate is high, the product is single, the separation and purification are simple, the production cost is saved, the cells are easy to recycle and are reusable, and the like.