The invention relates to a magnetic separable immobilized NAD kinase and a preparation thereof, which belongs to the technical field of the preparation of a superparamagnetism carrier material, and immobilization of NAD kinase. Superparamagnetism ferroferric oxide submicron particles are prepared in a solvothermal method, linked with iminodiacetic acid after the epoxidation and loaded with transitional metal ions, the NAD kinase with a His tag is immobilized by utilizing a metal chelating affinity principle, and the magnetic separable immobilized NAD kinase is obtained. The magnetic separable immobilized NAD kinase has the advantages that the epoxidation process is simple, no organic reagent and complex polymerization reaction step are needed, the NAD kinase immobilization reaction time is short, the selectivity is high, and the magnetic separable immobilized NAD kinase is easy to separate from a reaction system and can be repeatedly used.