The invention belongs to the technical field of genetic engineering and in particular relates to novel D-allulose 3-epimerase, DNA (Deoxyribonucleic Acid) for encoding the novel D-allulose 3-epimerase, an expression vector and a transformant containing the DNA and application of the enzyme to production of D-allulose. The D-allulose 3-epimerase is derived from thermoacidophile mesoaciditoga lauensis of a deep-sea spring and has relatively high conversion rate and thermal stability when being used for converting D-fructose into the D-allulose.