The invention relates to a method for preparing calcium-alginate-immobilized marine bacterium MP-2 esterase. Sodium alginate and marine bacterium MP-2 esterase are dissolved in a buffer solution of glycin (NaOH) and then mixed evenly; and the mixture is dripped into CaCl2 solution for balling, standing, immobilization, washing and drying so as to obtain the graininess immobilized marine bacteriumMP-2 esterase. The method has the advantages of stable system, good compatibility, mild reaction and high activity. The calcium-alginate-immobilized marine bacterium MP-2 esterase can be used as an ethyl caproate catalyst, has high synthesis conversion rate, can be used repeatedly and has wide application prospect.